Syrian authorities told international mediator Kofi Annan they had started withdrawing troops from three areas as part of a peace plan to end more than a year of fighting with rebels, his spokesman said.

But the report was undermined by news of fresh clashes between government forces and insurgents in another area in a town near the capital Damascus.

Fighting shows no sign of abating even though Syrian President Bashar Al-Assad agreed more than a week ago to a six-point peace plan drawn up by Annan, the joint UN-Arab League envoy to Syria.

"Yes they have told us that they have begun withdrawing troops from certain areas," Annan's spokesman Ahmad Fawzi told a news briefing in Geneva. "They have specified three cities - Deraa, Idlib and Zabadani."   

Fawzi said UN member states were being asked to provide troops for a ceasefire monitoring mission, to be deployed in Syria after April 10.

Media reports that 200 to 250 unarmed monitors would be deployed were "not very far off", he told journalists, adding the force would be deployed incrementally.

Fawzi said the mediators were trying to verify the reported withdrawals. An advance team sent by Annan was due to arrive in Damascus on Thursday to begin discussing their full deployment, which requires a UN Security Council resolution.

The peace plan set out by Annan, a former UN Secretary-General, sets a deadline of April 10 for withdrawing troops and heavy weaponry, followed within 48 hours by a halt to the fighting by both sides.

"What we expect on the 10th of April is that the Syrian government will have completed its withdrawal from populated centres, the withdrawal of military units from populated centres, that it would have stopped moving any military units into cities and that we begin a 48-hour period during which there will be a complete cessation of all forms of violence by all parties with 48 hours that includes of course the Syrian opposition and the Syrian government," Fawzi said.

"So the clock starts ticking on the 10th for both sides to cease all forms of violence," he added.

Annan would hold talks in Tehran on April 11 with senior Iranian officials on Syria, he said, referring to Syria's major ally in the region.

Meanwhile, Turkey said more than 1,600 Syrians have fled to Turkey in the last two days to escape what activists said was Syrian army shelling of villages near the northern Syrian towns of Idlib and Aleppo.

The numbers fleeing were the highest since March 15 when around 1,000 Syrians entered Turkey in one day. Since then, around 300 to 400 Syrians have fled each day.

Turkish leaders have said a flood of refugees or massacres of civilians by Syrian troops near its border could force them to act to prevent a humanitarian disaster.

Turkish Prime Minister Tayyip Erdogan said last month that setting up a "safe" or "buffer" zone along the border was among the options his government was considering. But that would mean sending in troops to secure the area, which could lead to confrontation between Syrian forces and the Turkish army, the second biggest in Nato.

Turkey's disaster and emergency management authority said 1,622 Syrians had fled to Turkey in the last two days, bringing the total number there to 21,285, of which 65 were in hospital.

Turkey-based Syrian opposition activists Omar Al-Kilani and Muthana Barakat attributed the influx to the Syrian military bombarding some 10 villages around Idlib and Aleppo in the run-up to April 10, the date set by peace envoy Kofi Annan for a Syrian troop withdrawal from restive cities. - Reuters