(CNN) -- Russian President Vladimir Putin warned the West on Sunday against arming Syrian rebels "who kill their enemies and eat their organs," referencing a widely circulated video that purports to show a rebel fighter eating the heart of a dead soldier.
Putin's comments signaled a clear disapproval of a U.S. plan to increase military support to Syrian rebels, and his warning came just one day before he was to meet with U.S. President Barack Obama for talks at the Group of Eight summit in Northern Ireland where Syria is expected to top the agenda.
"I believe you will not deny that one should hardly back those who kill their enemies and eat their organs. ... Do you want to support these people? Do you want to supply arms to these people?" Putin asked, speaking to reporters in London after meeting with British Prime Minister David Cameron.
The video referenced by Putin first surfaced online in May and generated outrage. The video, which was posted by a group loyal to President Bashar al-Assad, also raised questions abut the credibility of the rebels despite widespread condemnation of the act by the opposition.
Putin said those actions do not represent the "humanitarian and cultural values" of Europe or Russia.
"If we speak calmly, in a businesslike fashion, let me draw your attention to the fact that Russia supplies arms to the legitimate government of Syria in full compliance with the norms of international law," he said. "We are not breaching any rules and norms. Let me emphasize that: we are not breaching any rules and norms, and we call on all our partners to act in the same fashion."
Russia has been at odds with the United States, the UK and others over how to bring an end to the bloodshed in the civil war that has raged in Syria for more than two years, a conflict that the United Nations estimates has left more than 92,000 people dead and millions displaced.
Russia and Syria have an alliance dating back to the Cold War, and Moscow has been one of the leading weapons suppliers for al-Assad's government.
Obama is expected during his meeting with Putin to make his case for increasing support to the rebels. Obama's administration announced the move last week after it said Syria crossed a "red line" with the use of chemical weapons, including sarin gas, against the opposition.
Obama has not detailed the increased military support, but Washington officials told CNN that the plan includes providing small arms, ammunition and possibly anti-tank weapons to the rebels.
World leaders have put enormous pressure on al-Assad to end the war and step down, and U.N. Security Council efforts to take action have been repeatedly blocked by Russia and China.
Cameron, meanwhile, told reporters that Britain had not decided whether to provide weapons to rebels but was providing technical assistance and training alongside the United States, France and its other allies.
"I'm in no doubt that responsibility lies with President Assad. It is the onslaught that he is inflicted on his own people which is the primary cause of the suffering, the humanitarian catastrophe and the deaths we have seen," he said.
Putin told reporters that he hoped the G8 summit would provide an avenue that would allow him to help broker a peace deal to end the Syrian conflict. He said he believed both sides were responsible for the bloodshed.
Cameron acknowledged that he and Putin have deep differences on the issue of Syria but said they agree that it will take political and diplomatic efforts to help end the carnage.
Putin did not address Russian concerns that the United States may attempt to enforce a no-fly zone over Syria, using F-16 fighter jets and Patriot missiles based in Jordan.
On Saturday, Russian Foreign Minister Sergey Lavrov warned the United States against taking such action, saying it would be a violation of international law, according to Russian state broadcaster Russia Today.
Russian television reported that Lavrov's comments followed speculation in the media that a no-fly zone could be imposed through the deployment of the missile systems and fighter jets sent by the United States to global military drills in Jordan.
Those reports followed news that the United States had approved a Jordanian request to keep the fighter jets and missiles in the country after the conclusion of a joint military exercise.
U.S. State Department spokeswoman Jen Psaki has dismissed media accounts that Obama has decided on establishing a no-fly zone. Those reports are incorrect, she told reporters on Friday.
U.S. Deputy National Security Adviser Ben Rhodes also addressed the matter Friday when he was asked how difficult it would be to establish a no-fly zone.
"In Syria, when you have the situation where regime forces are intermingled with opposition forces, they're fighting in some instances block by block in cities. That's not a problem you can solve from the air," he said.
Syrian rebels have pleaded for anti-tank and anti-aircraft weapons, saying they are outgunned by al-Assad's miltary.
In recent weeks, the rebels have suffered a series of devastating setbacks, including the loss of the stronghold of Qusayr near the Syria-Lebanon border, that coincide with the arrival of Hezbollah fighters who have been reinforcing government troops.
In recent days, al-Assad's military and the Hezbollah fighters, backed by Lebanon and Iran, have been battling rebels for control of Aleppo, Syria's largest city.
CNN's Saad Abedine and Igor Krotov contributed to this report.