ISTANBUL (AFP) - Syrian opposition movements announced the formation of a "historic" united front against President Bashar al-Assad's regime at a meeting in Turkey on Sunday. Syrian troops, meanwhile, have taken control of the central city of Rastan after sending in 250 tanks to quell clashes between the army and deserters, human rights activists said. "The Syrian National Council reunites the forces of the opposition and the peaceful revolution," Paris-based academic Burhan Ghalioun told reporters in Istanbul, announcing the new umbrella movement which he called "historic." Uniting groups across the political spectrum, "it represents the Syrian revolution both inside and outside the country," he said. "It works to mobilise all categories of people in Syria and give the necessary support for the revolution to progress and realise the aspirations of our people for the overthrow of the regime, its symbols and its head," he said. Ghalioun said the SNC was "open to all Syrians." The SNC called on "international organisations to assume their responsibility toward the Syrian people and to work to protect them from the war declared against them, to halt ... the dangerous human rights violations." But "the council rejects any outside interference that undermines the sovereignty of the Syrian people," he added. Ghalioun is to chair the SNC, whose board will include Bassma Kodmani as spokeswoman, Mohammed Riyad al-Shaqfa of the Muslim Brotherhood and representatives of the so-called Damascus Declaration for reform. The new grouping is to hold a general assembly of 190 members at the beginning of next month, "probably in Turkey," Kodmani said. The SNC, which is to elect a president, will have a 29-strong general secretariat representing seven Syrian opposition factions. SNC member Hassan Hashimi said they would comprise six members of the Local Coordination Committees, five Brotherhood and tribal representatives, four of the Damascus Declaration and four for a liberal grouping led by Ghalioun. The remaining members of the secretariat would be five independents, four Kurds and a Christian, he said. The separate opposition factions will also be represented in a seven-strong executive committee, Hashimi said. Representatives of Syria's six-month-old protests and opposition met at the weekend against the backdrop of an uprising which the UN says has cost at least 2,700 lives since it erupted in mid-March. On the ground, the Syrian Observatory for Human Rights said the army had "taken complete control of Rastan, and 50 tanks left on Sunday" the town in Homs province, 160 kilometres (100 miles) north of Damascus. "Many houses have been destroyed there and the humanitarian situation is very bad," the Britain-based rights watchdog said. "We have information that dozens of civilians were killed and buried in the gardens of houses as the army shelled the town," it added. Officers who had deserted announced their "retreat from Rastan" in a statement on Friday night. "Because of major reinforcements and the weapons used in Rastan by Assad's gangs... we have decided to withdraw in order to better wage the struggle for liberty," the statement said.