The United Nations has ordered the end of its observer mission in Syria, and said that it would withdraw its staff within the next few days."The conditions to continue UNSMIS were not fulfilled,” said Gerard Araud, France’s ambassador to the UN, referring to the mission by its acronym.Edmond Mulet, from the UN peacekeeping department, told reporters that the mission would "come to an end” at midnight on Sunday.Earlier this year, the United Nations authorised sending up to 300 unarmed military observers to Syria to monitor a ceasefire that UN-Arab League envoy Kofi Annan negotiated with president Bashar al-Assad.But hostilities have only worsened since then, and the UN mission suspended its patrols on June 15, leaving the observers largely confined to their hotels.As of Thursday, the number had been cut to 101 observers and 72 civilian staff. Mulet said the last observer would leave Damascus on Friday next week.Brahimi ‘accepts’ mediator roleThe Security Council did back a plan by UN secretary-general Ban Ki-moon to start a political liaison office in Damascus to monitor events.Mulet told reporters it would probably be between 20 and 30 people, with political, humanitarian and military experts taking part. He added that Assad had approved setting up the office.Vitaly Churkin, the Russian ambassador at the UN, said an action group will meet on Friday to call for an end to the violence. Russia did not want to wind down the monitoring mission."We believe that those members of the council who insisted that the UNSMIS can’t continue did not really show a commitment to ending hostilities,” Churkin said.Veteran Algerian diplomat Lakhdar Brahimi has agreed in principle to replace Annan as the international mediator on Syria, UN sources said on Thursday.Annan is stepping down at the end of August after six months in the post because he said his Syria peace plan was hampered by a divided and deadlocked UN Security Council.Diplomats told the Reuters news agency on condition of anonymity that Brahimi,  who has previously served in Afghanistan and Iraq, had been undecided for days about whether to accept the offer of the post from Ban, did not want to be seen as a mere replacement of Annan but wanted an altered title and mandate. It was not clear when the official announcement would be made, envoys said.Some of the worst recent violence came in the rebel-controlled town of Azaz, about 45km north of Aleppo, where air attacks by the Syrian government killed at least 30 people. Researchers from Human Rights Watch put the death toll higher, at more than 40, with more than 100 wounded.