A second team of international inspectors arrived in Damascus Thursday to help supervise the destruction of Syria's chemical arsenal under the terms of a UN resolution.

Three UN vehicles carrying inspectors earlier departed from their Damascus hotel en route to an undisclosed location, as the dangerous mission to eradicate chemical arms in the hostile environment of a civil war continued.

Michael Luhan, a spokesman for the Organisation for the Prohibition of Chemical Weapons in The Hague, said 12 new experts arrived, bringing the total number to 27.

He said an "advance team" of 19 arrived last week but that four had since returned to The Hague.

Last week the experts began supervising the destruction, by Syrian authorities, of missile warheads, aerial bombs and chemical mixing equipment.

Syrian television released footage Tuesday of inspectors in protective gear and gas masks taking readings and applying labels bearing the OPCW logo.

The OPCW plans to inspect 20 sites in the coming weeks, including some in dangerous areas where fighting has raged between the army and rebels seeking the overthrow of President Bashar al-Assad.

Syria, which is believed to have 1,000 tonnes of sarin, mustard gas and other banned chemicals at some 45 sites, agreed to give up the arms under a rare US-Russian deal.

The inspectors are tasked under a UN Security Council resolution with destroying the arsenal by mid-2014.

The agreement was hammered out in the wake of August 21 sarin gas attacks on the outskirts of Damascus that killed hundreds of people and prompted Washington to threaten military action against Syria.

The Syrian government denied responsibility for the attacks, but agreed to turn over its chemical arsenal, averting threatened US military strikes.

Since the outbreak of the Syrian uprising in March 2011 more than 115,000 people have been killed and millions more displaced from their homes.