Opponents of President Bashar al-Assad mobbed the UN's advanced monitoring team Sergei Lavrov, Russian foreign minister, called for a thorough investigation into the killings. "Both sides participated in the killing of civilians," he told a press conference after a meeting in Moscow with William Hague, UK foreign secretary, on Monday. Mr Hague, however, said responsibility for the killings clearly lies with the Syrian government, which he said has in the past shown it is prepared "to commit atrocities and then blame those atrocities on someone else," he said. The spat over responsibility for the killings has laid bare growing fissures between Russia, which champions President Assad, a longtime ally, and the west, which would like to see Mr Assad's removal as part of a political settlement to the violence. In March both sides signed a peace plan prepared by Mr Annan that calls for a negotiated political settlement to the conflict. US and European officials say this process must lead to the departure of President Assad and new elections. For us it's not the most important thing who is in power in Syria. For us the main thing is to provide for an end to the violence," Mr Lavrov said. He also charged that many western politicians were not interested in the success of the Annan plan. "They are waiting for the Annan plan to fail, so they can say Assad has deceived everybody, that he has not fulfilled his obligations and therefore we need to support the military opposition," said Mr Pushkov, adding that western support for the Syrian opposition destroys any incentive for them to negotiate. While some western officials saw the Annan plan as a sign that Russia's position is softening, Mr Lavrov's and Mr Pushkov's comments appear to signal the opposite. The Syrian conflict is seen in Russia through the prism of Libya, Iraq and Yugoslavia, in which Russia lost valuable allies to US-led military interventions. In the Kremlin's often conspiratorial mindset, the human rights disasters which preceded these invasions were trumped up by the west with the help of a compliant media. At Monday's press conference, Mr Lavrov explicitly drew such a link. He compared the Houla tragedy with the massacre in the Kosovon town of Rachak in 1999 which became the rallying cry for Nato's bombardment of Serbia that year. He said an EU fact finding mission to Yugoslavia after the war had concluded that those killed in Rachek were not civilians but guerrillas killed in combat. "We are urging everyone to investigate objectively what happened (in Houla) before leaping to conclusions," he said. Russia's intake of the Syrian tragedy has a distinctly pro-Damascus spin. Russian state TV more often than not is heavily weighted towards Syrian officials extended denials of complicity in attacks on civilians. The change in power in the Kremlin this month is also likely a reason many analysts sense a harder Russian line. Since hard line Vladimir Putin took over the presidency from his more west-friendly counterpart Dmitry Medvedev on May 7, he has sought to project a distrust and disdain of Washington, which he publicly accused of trying to overthrow him last winter during protests. Earlier this month he cancelled his attendance at a G8 summit and a meeting with President Barack Obama in the US at the last minute, citing a busy schedule.