United Nations military observers have left Damascus after a four-month mission in which they became helpless spectators of Syria's spiralling conflict.

Seven UN cars were seen leaving a Damascus hotel this morning, carrying some of the last members of a mission that at its height deployed 300 observers across the country.

The unarmed monitors suspended operations in June after coming under fire and most have already left the country.

A small "liaison office" remains in Damascus in case a chance for a political settlement to the bloodshed emerges.

Battling a 17-month-old uprising against his family's 42-year rule, President Bashar al-Assad has used fighter jets and helicopter gunships to pound rebel strongholds.

Insurgents have stepped up their attacks, hitting tanks, military convoys and security buildings.

The mandate of the monitoring mission, known as UNSMIS, expired last night after diplomats at the UN said conditions for continuing operations had not been met.

The last monitors are expected to be out of the country by Friday.

After a brief lull, violence intensified during the monitors' presence in Syria and at least 9,000 people have been killed since they arrived to oversee a ceasefire declared on 12 April by former UN-Arab League mediator Kofi Annan.

The truce never took hold and at least 18,000 people have now been killed in Syria since the anti-Assad revolt began.

Around 170,000 people have fled the country, according to the UN, and 2.5m need aid in Syria.

Syrian government forces have reportedly shelled Darya, a suburb of Damascus, and the cities of Aleppo and Daraa.

Rights groups and activists have claimed that 30 people were killed in today's attacks.

Turkey calls for 'safe zone' for refugees

Meanwhile, Turkey’s foreign minister was quoted as saying the UN may need to create a "safe zone" within Syria to accommodate a growing number of refugees from the fighting there.

Turkey, already hosting nearly 70,000 Syrians fleeing the 17-month-old revolt may soon be unable to cope, Ahmet Davutoglu told the Hurriyet newspaper.

"If the number of refugees in Turkey surpasses 100,000, we will run out of space to accommodate them. We should be able to accommodate them in Syria. The United Nations may build camps in a safe zone within Syria's borders," he was quoted as saying.

Syrian rebels have expanded the territory they hold near the Turkish border in the last few weeks and opposition groups have said they need the protection of no-fly zones and safe havens patrolled by foreign forces.

US Secretary of State Hilary Clinton said last week that the US and Turkey were looking at all measures to help the insurgents, including a no-fly zone, although no member of the UN Security Council has formally proposed such a move and the option has gained little traction so far.

A no-fly zone and a NATO bombing campaign helped Libyan rebels overthrow Muammar Gaddafi last year.

The West has shown little appetite for repeating any Libya-style action in Syria, and Russia and China strongly oppose any such intervention.

Turkey began handing out food and other humanitarian aid to Syrians on the border on Saturday.

Mr Davutoglu was quoted as saying Turkey would attend a ministerial meeting of UN Security Council members planned for 30 August and would abide by any decisions made at the meeting.