A team of UN experts investigating the alleged use of chemical weapons in Syria crossed into Lebanon on Monday at the end of their mission, an AFP correspondent said.

The team, which arrived in Syria last Wednesday, is due to submit a report next month about seven alleged chemical weapons attacks during the conflict in Syria.

A second, separate group of inspectors from the Hague-based Organisation for the Prohibition of Chemical Weapons is also expected to arrive in Syria on Tuesday.

That team will be inspecting Syria's chemical arsenal, which Damascus has agreed to turn over for destruction under a US-Russia deal now enshrined in a UN Security Council resolution.

The UN experts were on their second mission to Syria, after a first trip in August when they confirmed the use of sarin in the outskirts of Damascus.

The deadly nerve agent was used in an August 21 attack while the experts were in Damascus on a mission originally intended to investigate other alleged chemical weapons attacks.

The Syrian regime and the rebels battling to overthrow it have traded accusations of chemical weapons use during the country's conflict.

Other alleged attacks the UN team probed include a March 19 incident in Khan al-Assal, in Aleppo province of northern Syria, an April attack in the Sheikh Maqsud neighbourhood of Aleppo city, and Saraqeb in the northwestern province of Idlib on the border with Turkey.

In addition to this, the team investigated alleged attacks on August 22 in Bahhariyeh, near Damascus, on August 24 in the Jubar district of the capital, and a seventh incident reported in Ashrafiyeh Sahnaya in Damascus province on August 25.

UN officials had said the team would not visit Khan al-Assal, Saraqeb or Sheikh Maqsud, noting the alleged attacks there took place in March and April and the bio-medical evidence will have mostly degraded.