The Syrian army pressed attacks on rebels on Tuesday, bombarding the city of Douma near Damascus, and Turkey said it had scrambled F-16 fighters the previous day after Syrian helicopters flew near its border.

Turkey's armed forces command said the jets took off on Monday when Syrian transport helicopters were spotted flying near the frontier, without entering Turkish air space. It was the third day in a row that Turkey had scrambled its F-16s.

Syrian President Bashar al-Assad told a Turkish daily he wished his forces had not shot down a Turkish jet last month and that he would not allow tensions with Turkey to lead to war.

The downing of the Turkish F4 in disputed circumstances has aggravated hostility between Damascus and Ankara, which has raised its military profile to try to keep Syrian helicopters from Turkey's border zone where rebels and refugees are camped.

'We learned it belonged to Turkey after shooting it down. I say 100 percent 'if only we had not shot it down',' Turkey's Cumhuriyet daily quoted Assad as saying.

A Syrian general and 84 soldiers were the latest to defect and flee to Turkey on Monday. But army and government defections have so far failed to shake Assad's 12-year grip on power.

More violence erupted on Tuesday in a 16-month conflict that opposition leaders say has killed more than 15,000 people.

'There was heavy shelling all morning, now it has calmed down a bit but the siege of the city continues,' said Abu Rami, an opposition activist in Homs, which has borne the brunt of an army onslaught on rebel strongholds.

'We are living with little food and little water,' he said.

The army shelled towns and villages near Douma to which the embattled city's residents had fled at the weekend, according to Omar Hamzeh, spokesman for the revolutionary council of rural Damascus. He said at least six people had been killed.

Syrian helicopters bombarded Douma on Monday, activists said.

Diplomacy has so far failed to stem the bloodshed. World powers agreed at the weekend to back talks on a transitional government. But they failed to narrow differences between the West and Russia over Western demands that Assad must go.

Turkey, which has long demanded the Syrian leader's removal, said Assad could play no part in a transitional government, but suggested the Syrian opposition would do well to accept envoy Kofi Annan's internationally endorsed proposal.

'Our task is not to pressure the opposition or to persuade them of something,' Davutoglu told Sky News Arabia in Cairo, where opposition groups were meeting for a second day.

He said Annan's mediation role meant the opposition would not have to negotiate with Assad under the transition plan.

'Thus I believe that accepting the Geneva statement would be a positive thing from the opposition,' he said, according to an Arabic transcript of his remarks provided by Sky News Arabia.

His Russian counterpart, Sergei Lavrov, said Syrian opposition leaders would hold talks in Moscow next week, but it was not clear if they would include any from the mainstream Syrian National Council (SNC) backed by the West and Turkey.

'We will use this coming meeting with yet another Syrian opposition group to continue work to end violence and start Syrian dialogue between the government and all groups of the Syrian opposition as soon as possible,' Lavrov said.

Neither Assad nor those trying to topple him have shown much interest in peaceful compromise. Instead, they seem to be digging in for a winner-take-all struggle as Syria slides deeper into a civil war with sectarian overtones.

Syria's chief of staff, General Fahd Jassem al-Freij, said the nation was at war with conspirators seeking its destruction.

The official news agency Sana quoted him as saying Syria had dealt positively with all Arab and international initiatives to find a settlement, but its enemies had replied with escalation on the ground, coupled with media frenzy to disrupt normal life.

The rebel Free Syrian Army, spearheading the armed struggle against Assad, has boycotted the SNC gathering in Cairo, where the Arab League was urging Islamist and secular groups to end their quarrels and form a credible alternative authority.

Syrian opposition leaders have said Assad's removal must be the starting point for any resolution to the conflict because of the suffering he has inflicted on the Syrian people.

New York-based Human Rights Watch issued a report on 'an archipelago' of Syrian state torture centers, citing accounts of victims who said they were beaten, burned with acid, sexually assaulted or had their fingernails torn out.

A meeting in Paris on Friday of the 'Friends of Syria' grouping may see the US come under pressure from Saudi Arabia and Qatar, to do more to help the rebels, and from Turkey to play a bigger role.

Washington has long worried about the wisdom of backing Syria's opposition, which it sees as ill-organized, disparate and much too close to al Qaeda-linked militants.

'We're concerned about pouring more weapons into an already over-militarized situation,' US State Department spokeswoman Victoria Nuland said on Monday. 'We've made our decision.'

UN human rights chief Navi Pillay warned the same day that arms supplies to the rebels and the government were aggravating the conflict.-Reuters