UN experts charged with starting the process of verifying and eliminating chemical weapons have arrived in Syria.

A convoy of about 20 United Nations vehicles carrying the team arrived in Damascus shortly after 5pm (3pm Irish time), witnesses said.

The mission, endorsed by the UN Security Council, is expected to continue until at least mid-2014.

It was hammered out by the United States and Russia after a 21 August chemical weapons attack in Damascus prompted US threats of air strikes against the Syrian government.

Hundreds of thousands of people have died in Syria's conflict, which began in early 2011 with peaceful demonstrations seeking more democracy, but has deteriorated into sectarian civil war.

The Syrian Observatory for Human Rights today said over 115,000 people had been killed in the civil war, including tens of thousands of soldiers, rebels and civilians. 

The figure suggests that around 5,000 people had died in September alone.

It indicated that the bloodshed has not been slowed by the international deal for the elimination of Syria's chemical weapons.

The British-based Observatory, which monitors violence through a network of activists, medical and military sources around Syria, said about 47,000 soldiers and militia fighters loyal to President Bashar al-Assad had been killed.

Rebel fighters, including army defectors, accounted for around 23,000 of the dead, the Observatory said.

More than 41,000 civilians have been killed, including 6,000 children and 4,000 women.

The toll includes 3,000 unidentified people, according to the Observatory, which says it documents deaths by obtaining film and photographs of bodies and seeking to confirm identities through family, medics and activists.