The group, led by chief expert Ake Sellstrom, flew to Beirut in Lebanon and travelled by overland convoy via the Masnaa border post to Damascus on Wednesday.

US President Barack Obama on Tuesday demanded tough Security Council action against Syria as the conflict there dominated debate at the annual UN General Assembly.

Sellstrom's inspectors are expected to examine the alleged use of chemical weapons some 14 times in the 30-month conflict that is estimated to have killed more than 110,000 people.

After a preliminary visit last month, his team concluded in a report presented on September 16 that banned chemical weapons had been widely used in fighting between the Syrian government and foreign-backed militants.

There was clear evidence that sarin gas was used in an attack in the Eastern Ghouta neighborhood near Damascus on August 21, the report said.

Sellstrom pointed out that the report was only an interim document, and that other allegations needed to be examined.

Hundreds of people were killed and scores of others injured in the chemical attack which took place in the suburbs of Damascus on August 21.

The militants operating inside Syria and the foreign-backed Syrian opposition claimed that the deadly attack was carried out by the army.

Damascus, however, has strongly denied the accusation, saying it was a false-flag operation carried out by Takfiri groups in a bid to draw in foreign military intervention.

Following the chemical attack, the US called for punitive military action against Damascus. The Syrian government averted possible US aggression by accepting a Russian plan to put its chemical arsenal under international control and then have them destroyed.

HH/HH