Syria's foreign minister says Damascus has begun withdrawing some of its troops from cities in line with a UN-backed peace plan to end a year of bloodshed in the country. Walid al-Muallem, speaking on Tuesday after meeting his Russian counterpart in Moscow, said Syria wanted a say in the composition of an international team to observe implementation of a ceasefire in the country. “We have already withdrawn forces and army units from several Syrian provinces,'' Muallem said. "An end of violence must be simultaneous with the arrival of the international observers." Brokered by Kofi Annan, the joint UN-Arab League envoy to Syria, the six-point peace plan required Syrian forces to pull back from protest centres by Tuesday. But activists say that Syrian forces have attacked two towns as the deadline passed. Shelling was reported in the northern village of Marea and mortar fire in the city of Homs, according to the Associated Press news agency. Muallem said his government wanted guarantees from Annan that the opposition fighters would commit to a ceasefire. "We will not ask the terrorist groups, which are killing, kidnapping and destroying infrastructure, for guarantees," he said. "We want Annan to give us these guarantees." 'Infringing border' For their part, Russia and China, who have twice shielded Syria from UN sanctions, called on the government of Bashar al-Assad as well as the opposition to work towards Annan’s proposed truce. Sergey Lavrov, the Russian foreign minister, said Syria's government “could have been more active and decisive'' in implementing the peace plan”. And Liu Weimin, the Chinese foreign ministry spokesman, said his country hopes the Syrian government and opposition “stay with their commitment to the ceasefire and withdrawal, and create favourable conditions for easing the tension in Syria and pushing for a political resolution for the Syria issue". Assad's crackdown on the uprising, that has brought clashes with an increasingly armed opposition, has killed more than 9,000. The fighting has also spilled over Syria's borders and Recep Tayyip Erdogan, Turkey's prime minister, has accused Syria of infringing its border. A day after Syrian forces opened fire across the border, killing two people in a refugee camp, Erdogan said his country is considering what steps to take in response, including measures “we don't want to think about.'' Turkish authorities said on Monday that Syrian forces fired across the border into a refugee camp, wounding at least six people. Al Jazeera's Anita McNaught, reporting from Antakya in southern Turkey, said the incident signified "a remarkable escalation in tensions" in an already tense cross-border area.