Russian President Vladimir Putin alluded to a graphic video, purporting to show a Syrian rebel commander biting into the heart of a soldier, during a joint press conference with the Prime Minister.
He made the point to justify Russia's opposition to arming Syrian rebels, saying that both sides in the conflict had "blood on their hands".
Putin also said he hoped the G8 Summit would have a "positive influence" on international efforts to end the conflict in Syria.
David Cameron admitted there were 'big differences' between the UK and Russia on the Syria conflict, but insisted they could be overcome
Russia warned the West that arming Syrian rebels could escalate violence as David Cameron backed a US assessment of a need for involvement.