Russia further backed away from its support of Syrian President Bashar Assad, saying his government bears the main responsibility for the violence in the country and calling for a full investigation into its role in the deaths of more than 100 civilians in Houla.
"Both sides have obviously had a hand in the deaths of innocent people, including several dozen women and children. This area is controlled by the rebels, but it is also surrounded by government troops," Russian Foreign Minister Sergey Lavrov said after talks in Moscow with visiting British Foreign Secretary William Hague.
Lavrov spoke a day after Russia agreed to join the rest of the UN Security Council in blaming the Syrian government for attacking residential areas in Houla, a collection of villages near the central city of Homs. The council, however, avoided saying who was responsible for the massacre of at least 108 men, women and children.
Lavrov said there was no doubt that government forces had used artillery and tanks to shell Houla, but he noted that many of the dead appeared to have been shot at close range or tortured.
"The guilt has to be determined objectively," he said. "No one is saying that the government is not guilty, and no one is saying that the armed militants are not guilty."
In some of Russia's harshest criticism of Assad to date, Lavrov said his government "bears the main responsibility for what is going on" because it is failing to provide for the security of Syrian citizens. He hedged the criticism by claiming that Syria's government is facing an increased threat from terrorists, whose bombings have the "clear signature of al-Qa'ida."
Alexei Malashenko, a Middle East expert with the Carnegie Moscow Center, said Russia can no longer defend Assad's government and may be warning him that he needs to change his approach.
"Bashar Assad is driving himself and Russia into a corner," Malashenko said. "If this goes on, Russia will have no other option" but to pull its support. "Bashar has definitely gotten the sense that he may lose Russia's sympathy and he may step back a bit."
Lavrov and Hague both called for greater efforts to implement a peace plan put forward by special envoy Kofi Annan, who arrived in Damascus today for talks with Assad and other senior Syrian officials. Annan's six-point plan calls on both sides to respect a cease-fire.
"It's right, as Sergey Lavrov has just done, to call on all parties to cease violence, and we are not arguing that all violence in Syria is the responsibility of the Assad regime, although it has the primary responsibility for such violence," Hague said.
Lavrov added that "we don't support the Syrian government, we support Kofi Annan's plan."
The Russian envoy called for everyone in the international community to exert more pressure on both sides to implement Annan's plan, saying it was not clear from talks with opposition members that they were getting the message that the plan had full international support. He said talk about the need for Assad to step down cast doubt on the West's commitment to the Annan plan and encouraged the opposition to keep up the fight.
Hague, however, confirmed that Britain still believes Assad should stand aside.
"But the important thing is that the Annan plan is pursued in whatever way it can be pursued," he said. "The alternatives are the Annan plan or ever-increasing chaos in Syria, and a descent closer and closer to all-out civil war and collapse."
China on Monday also condemned the killings of civilians in Houla and called for an end to the violence, but gave no indication it was rethinking its strategy toward the fighting in Syria.
Chinese Foreign Ministry spokesman Liu Weimin said that Beijing fully supports Annan's mediation efforts and the UN monitors.
The protests against Assad began in March 2011 and turned into an uprising after his government responded with a violent crackdown on dissent. The UN estimated that at least 9,000 people were killed in the first year of the conflict, but hundreds more have been killed since then.