Syria's government has agreed to accept the peace plan put forward by the United Nations and Arab League envoy, Kofi Annan, his spokesman has said. Mr Annan considered it "an important initial step that could bring an end to the violence", but that implementation of his plan was key, Ahmed Fawzi added. However, the main opposition coalition is sceptical and has questioned whether the government will honour its pledge. Meanwhile, the UN said more than 9,000 people had been killed in the uprising. Robert Serry, the Special Co-ordinator for the Middle East Peace Process, told the Security Council that violence on the ground had "continued unabated". "It is urgent to stop the fighting and prevent a further violent escalation of the conflict," he added. In other developments: • Clashes between Syrian security forces and armed rebels have spilled across the border with Lebanon, witnesses and Lebanese security officials say • Syria's opposition groups are meeting in Istanbul to try to achieve a more united front • President Bashar al-Assad has visited the former rebel stronghold Baba Amr in Homs, which troops entered earlier this month after nearly four weeks of bombardment left an estimated 700 people dead • Yakin Erturk has resigned from a UN commission of inquiry looking into alleged human rights abuses, citing lack of access to Syria • Turkish Airlines is stopping flights to Syria after Turkey's closure of its embassy in Damascus. 'Critical juncture' Speaking after it was announced that the Syrian government had accepted his peace plan, Mr Annan thanked countries that have supported his attempts to mediate in the conflict. He is currently in Beijing for talks with Chinese Premier Wen Jiabao. Mr Wen offered his support for Mr Annan's strategy, saying the situation was "at a critical juncture", and "your mediation efforts will lead to progress". At the weekend Russia also offered its support. The two countries had been heavily criticised after vetoing two UN Security Council resolutions condemning the violence. Mr Annan's six-point plan calls for President Assad's government to pull troops and heavy weapons out of population centres, and for all parties to allow for a daily two-hour pause to the fighting in order for humanitarian aid to reach affected areas. The plan also requests that the authorities release those detained in the uprising. However, it does not impose any deadline for Mr Assad, or call for him to leave power. The main opposition coalition, the Syrian National Council (SNC), which is seeking to agree a "national pact" of common objectives with other opposition groups in Istanbul, gave a lukewarm response to the plan. "A peaceful transition means that the regime needs to be changed. And that starts with the removal of the head of the state," Basma Kodmani, a spokeswoman for the SNC, told the Reuters news agency. "Mr Annan's initiative for us should lead to developments of clear terms of reference for negotiation on the modalities of change. Not on whether the change should happen or not." "What we would like to see is the stopping of the killings," she added. "We would like to see protection of civilians, if there is a possibility even of a two hours of truce to begin with. I think we welcome that and we will certainly work to make that succeed." Mr Annan has written to President Assad urging him to put his commitments into immediate effect.