A senior aide to Syria's President Bashar al-Assad has flown to China for talks on the crisis, officials say. The Chinese foreign ministry said Bouthaina Shaaban would meet Foreign Minister Yang Jiechi later. The ministry said it was part of its effort to implement the UN's six-point peace plan. China has twice vetoed UN resolutions against the Assad regime. Meanwhile, UN humanitarian chief Valerie Amos is due to arrive in Syria to assess the flow of emergency aid. She is expected to ask for more visas for foreign aid workers as the Syrian Arab Red Crescent struggles to distribute food. The UN says an estimated two million Syrian civilians have now been affected by the crisis and more than one million have fled their homes. Tens of thousands of people have fled across Syria's borders into Turkey, Jordan, Lebanon and Iraq amid continuing violence across the country. In another development, foreign ministers of the Islamic Co-operation Organisation (OIC) have called for Syria to be suspended from the 57-nation bloc at an emergency two-day summit in Mecca, Saudi Arabia, which starts on Tuesday. Only ministers from Algeria and Iran, which is regarded as Syria's closest ally, were against the recommendation, reports say. "We certainly do not agree with the suspension of any OIC member," Iranian Foreign Minister Ali Akbar Salehi said after a preliminary meeting in the city of Jeddah on Monday. "We have to look for other ways, means and mechanisms for resolving conflicts and crises," he said. Downed jet Chinese foreign ministry spokesman Qin Gang said in a statement that China had always "actively balanced its work between the Syrian government and the opposition". He repeated China's call for the "practical implementation" of former UN envoy Kofi Annan's peace plan - now widely considered defunct - and for "an immediate ceasefire". "Receiving Shaaban in China is part of the above-mentioned work by the Chinese side," Mr Qin said, adding: "China is also considering inviting Syrian opposition groups in the near term to China." China, along with fellow UN Security Council permanent member Russia, has vetoed UN resolutions condemning the violent crackdown by Mr Assad's government. Correspondents say it wants to deflect criticism and show it is trying to develop a political solution to the Syrian crisis. In Syria, rebels clashed with government forces in the northern city of Aleppo and the capital Damascus on Monday, opposition groups said. Activist group the Local Co-ordination Committees said at least 64 people had been killed in Damascus and its suburbs. The UK-based Syrian Observatory for Human Rights said government forces had begun a new advance against rebels in Aleppo, which has seen fierce clashes in recent weeks. Syrian rebels also produced footage of a man they claim was the captured pilot of a fighter jet shot down in the east of the country. The Free Syrian Army (FSA) said it had shot the aircraft down near the Iraqi border. However, state media say the plane crashed because of "technical problems" and a search is under way to find the pilot.