According to the final report of a UN inquiry into chemical weapons use in Syria, the deadly nerve agent sarin was likely used in four locations in addition to the confirmed attack near Damascus in August.

"The United Nations Mission concludes that chemical weapons have been used in the ongoing conflict between the parties in the Syrian Arab Republic," the final report said.

The report, published Thursday and handed in to UN Secretary General Ban Ki-moon, examined seven alleged chemical weapons attacks and was carried out by a team of chemical weapons experts, led by Swedish professor Ake Sellstrom.

The team said that despite signs and witness testimonies pointing to chemical weapons being used, the lack of "primary" information prevented them from drawing conclusions independently.

The investigation found that evidence indicated chemical weapons were probably used in Khan al Assal outside the northern city of Aleppo in March, Saraqueb near Idlib in the northwest in April, and Jobar and Ashrafiah Sahnaya near Damascus, in August.

The last two locations out of the lacked information to confirm the allegations, according to the report.

The inspectors' task, however, did not mandate them to identify whether the government or opposition fighters were behind the attacks. President Bashar al-Assad's government and the opposition rebels have accused each other of using chemical weapons, and both have denied it.

Sarin crosses the line

UN investigation team leader, Sellstrom, released an initial report on September 16 which concluded that evidence collected in the Ghouta area of Damascus following an August 21 attack provided "clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used."

Graphic video footage from the attack showed dozens of people gasping for air and bodies of men, women and children lined up in make-shift hospitals. The US government said more than 1,400 people were killed in the attack.

The attack in Ghouta led to the threat of possible US military action, however a US-Russian brokered agreement was reached to eliminate Syria's chemical weapons by mid-2014. Al-Assad's government agreed to the plan and the process of destroying the country's arsenal is currently under way.

The UN experts tasked with the investigation were from the Organization for the Prohibition of Chemical Weapons (OPCW) and the World Health Organization. The OPCW was awarded the Nobel Peace Prize in October for its "extensive efforts to eliminate chemical weapons."

hc/jr (Reuters, AFP, AP)