"Su-25 jets hit a fortified IS position in the Tadmur area of Homs province," Moscow's defence ministry said, using the Arabic name for Palmyra.

"As a result of a direct strike, a fortification, an underground bunker and anti-aircraft artillery were destroyed."

Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights, also said that Russian planes had targeted Palmyra with strikes on Monday.

He said several strikes hit the city's historic citadel, but had no further details.

Khaled al-Homsi, an activist from Palmyra, also reported Russian strikes on the citadel on the western edges of the historical site.

"The extent of the damage could not be verified," he told AFP.

The Russian defence ministry previously said its warplanes had struck close to the ancient city but insisted that it avoided historic sites.

Syrian state television said in early October that Russian warplanes, acting in coordination with the Syrian air force, had struck IS targets "in and around" the city.

Elsewhere in Homs province, the Observatory said at least 10 people had been killed and more wounded in apparent Russian strikes on Al-Qaryatain, an IS-held town.

Russia did not specify when the strikes on Palmyra took place, but said its jets struck over 237 targets in Syria over the past two days in a statement on Monday.

Russian warplanes pounded sites belonging to the Islamic State and Al-Qaeda affiliate Al-Nusra Front "terrorist groups" in the Homs, Hama, Latakia, Damascus, Aleppo and Raqa provinces, Moscow said.

In Aleppo province, Moscow said it hit a training camp for foreign fighters and an improvised explosive device production plant, and destroyed two armoured vehicles in Hama province.

Russia's military said it also struck a key Al-Nusra Front command post on a strategic hill in the coastal Latakia region.

The latest raids came after broad international talks to end the conflict were held on Friday in Vienna.

For the first time, the meeting brought together all the main outside players in the crisis, including Russia and Iran, key allies of the government of President Bashar al-Assad.

Participants agreed to ask the United Nations to broker a peace deal between the regime and opposition -- which were not represented at the talks -- to clear the way for a new constitution and UN-supervised elections.

Russia has been bombing in Syria since the end of September to help troops loyal to Assad fight what it calls "terrorists".

The US and its allies in a separate coalition bombing IS say that Moscow is mainly targeting more moderate groups fighting Assad.

Without Congressional permission, public debate, or any attempt to rally the American public’s support, President Obama has ordered U.S. ground troops to a war zone, his most flagrantly unconstitutional war-making since he unlawfully helped to overthrow Muammar al-Qaddafi. “The United States is set to deploy troops on the ground in Syria for the first time to advise and assist rebel forces combating ISIS,” CNN reports. “The deployment of U.S. Special Operations forces is the most significant escalation of the American military campaign against ISIS to date.”

This should perturb even proponents of a U.S. war against ISIS

As Obama put it prior to the 2008 election: “The president does not have the power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.”

Now he is engaging in the very actions that he specifically declared to be illegal. And Congress is abdicating its responsibility to either empower him to wage war or to rein him in. Its passivity is enabling Obama to exceed the limits of his power in a way that has, in the past, led to failed wars as catastrophic as Vietnam and as recent as Libya.

Obama’s course “marks a decisive break in the American constitutional tradition,” Yale Law’s Bruce Ackerman argued long before any ground troops were deployed.

And beyond its illegality, it makes U.S. foreign policy less effective.

As law professor Ilya Somin explains in the Washington Post, “One of the main justifications for the Constitution’s requirement that presidents can only initiate a war if they have congressional authorization is to assure that any such war is backed by a large political consensus. If we decide to fight a war at all, it should only be in cases where there is widespread agreement that the war is justified and that we will do what is necessary to prevail. At least so far, the president’s war against ISIS has been a lesson in the dangers of launching a military intervention without that kind of political support.”

He acknowledges that the Obama Administration asked Congress to pass a new AUMF earlier this year. “But the draft it submitted to Congress had so many flaws that both Democrats and Republicans voiced strong objections, as did many academic experts,” he wrote. “Most Republicans do in fact support fighting ISIS. This is one of the few issues that Obama and GOP conservatives in Congress largely agree on. It should be possible for the two sides to come up with an AUMF that both can sign on to. Both the administration and Congress deserve blame for the failure to do so.”

Consider some of the ways that each are to blame.

There is little public debate about this illegal war-making—despite the fact that we’re in the midst of fiercely contested Republican and Democratic primaries—in part because the White House has been misleading the public about the extent of its actions. Even Friday, addressing special-ops troops sent to operate in Syria, White House Press Secretary Josh Earnest declared, “These forces do not have a combat mission.”

Secretary of Defense Ashton Carter has been more forthright.

Testifying last Tuesday about the American troop presence in Syria and Iraq, where a U.S. special forces commando was killed during a raid on ISIS earlier this month, he said that American troops deployed there “won’t hold back from supporting capable partners in opportunistic attacks against ISIL, or conducting such missions directly whether by strikes from the air or direct action on the ground.”

Fox News reports that U.S. forces have engaged in combat missions against ISIS in Iraq for the last year; Colonel Steve Warren told a press briefing in Bagdhad last week that “we’re in combat,” adding “I thought I made that pretty clear ... That is why we all carry guns. That’s why we all get combat patches when we leave here, that’s why we all receive an immediate danger badge. So, of course we’re in combat.”

A candidate who campaigns on that platform owes the electorate a frank explanation if he totally reverses himself once he is exercising power.

Why do journalists have to press exasperated military officials for these overdue acknowledgements as civilians in the White House obfuscate and dissemble? Many legislators apparently remain in the dark. “I don’t think Congress is always even close to fully knowledgeable as to what is happening,” Senator Bob Corker, the chairman of the Senate Foreign Relations Committee, told Eli Lake and Josh Rogin.

A few members of Congress, notably Senators Tim Kaine, Jeff Flake, and Rand Paul, have tried to fulfill their responsibility to determine how the war power should be used.

But other members of Congress know that the president is exceeding his constitutional authority to wage war and are urging him to exceed it even more aggressively.

The New York Times addressed that faction in an editorial:

The Pentagon continues to call the military campaign in Syria and Iraq an “advise and assist” mission, a characterization that was misleading when the campaign began and is now absurd. By incrementally increasing its combat role in a vast, complicated battleground, the United States is being sucked into a new Middle East war. Each step in that direction can only breed the desire to do more. Commanders will want to build on battlefield successes when things go their way, and they will be driven to retaliate when they don’t... But before contemplating a more forceful military plan, Congress and the administration must confront the fact that the current one, which includes airstrikes and support for select bands of rebels, lacks a legal framework and an attainable goal.

The first problem could be fixed if the White House and congressional leaders were willing to work together to set clear limits on what the Pentagon is allowed to do. Preposterously, the military campaign that began more than a year ago, and has cost more than $4 billion, is still being waged under the authority of the congressional authorization passed to pursue the perpetrators of the Sept. 11 attacks. With a few exceptions, lawmakers seem completely unconcerned that they are allowing a president to go to war without formal authorization from Congress. Instead, many are calling on the administration to take even bolder steps that range from establishing a no-fly zone over parts of Syria to using American firepower to oust Bashar al-Assad, the Syrian president.

The U.S. is ostensibly fighting on two different sides of the Syrian civil war: The Obama administration wants Syrian leader Bashar al-Assad to leave power and to defeat ISIS, one of several rebel groups fighting for control of Syria against al-Assad.

Russia and Iran also want to defeat ISIS, but want al-Assad to stay in power.

Al-Assad is a brutal dictator.

ISIS is an evil group that has perpetrated unimaginable atrocities, destabilized numerous countries, and made it hard to imagine anything worse in the areas that it controls. It is easy to understand why many observers believe that U.S. intervention would improve the world and advance or be consistent with our national interests—and why many others doubt our ability to improve Iraq and Syria, are averse to risking American lives to do so, and fear getting into a proxy war with Russia.

The gravity of what could transpire if the war goes wrong is precisely why Congress and the public ought to have come to a position through democratic debate and Madisonian institutions before the United States chose its present course.“History has shown us time and again ... that military action is most successful when it is authorized and supported by the Legislative branch,” Obama said in 2007. “It is always preferable to have the informed consent of Congress.” A candidate who campaigns on that platform owes the electorate a frank explanation, at the very least, if he totally reverses himself once he is exercising power.

Instead Obama just keeps pretending that he isn’t quite waging war.

If ISIS is worth fighting, Obama should make that case as persuasively as he can to Congress and the public, rallying the support that is necessary for successful wars.

And he should abide by the course set by the people’s representatives.

Come 2017, the nation will have a new president. Roughly half the country will mistrust his or her judgment. If you don’t want Donald Trump, Ben Carson, or Hillary Clinton empowered to start wars of their choosing without even asking Congress, the time to speak up is now, before John Yoo’s view of the Constitution is further entrenched. What George Will observed last autumn, long before recent escalations in Iraq and Syria, still goes. “Regarding war with the Islamic State,” he wrote, “the Constitution requires what prudence strongly recommends—congressional authorization.”