A new UN report states that in addition to the widely publicised chemical weapons attack on August 21 near Damascus, such weapons were probably used in four other locations in Syria between March and late August.
The report, published on Thursday, examined seven attacks in which chemical weapons use had been alleged.
In-depth coverage of escalating violence across Syria
"The United Nations Mission concludes that chemical weapons have been used in the ongoing conflict between the parties in the Syrian Arab Republic," noted the report by chief UN investigator Ake Sellstrom.
The UN Mission investigated seven instances of the possible use of chemical weapons.
The report cited "credible evidence" and "evidence consistent with the probable use of chemical weapons" in Ghouta, Khan al-Assal, Jobar, Saraqeb and Ashrafieh Sahnaya.
However, the UN said it could not corroborate their use in Bahhariyeh and Sheik Maqsoud. The report also found that chemical weapons were probably used on a small scale in Saraqeb and in Ashrafiah Sahnaya.
Sellstrom delivered his report on Thursday to UN Secretary-General Ban Ki-moon, who urged the elimination of the deadly weapons not only in Syria but across the world.
On Friday, Russia offered help to transport Syrian chemical weapons to a port in the country where they can then be removed aboard ships.
The report did not ascribe responsibility for the use of the weapons to the government or the rebels, as this was beyond the investigators' remit.
Amnesty slams EU on refugees
Meanwhile, in another report published on Friday by rights group Amnesty International stated that European leaders should "hang their heads with shame" over their treatment of Syrian refugees fleeing the country's brutal conflict.
The report states that European Union (EU) member states only offered around 12,000 places to Syrian refugees as part of the United Nations High Commissioner for Refugee's goal of securing 30,000 places.
|Amnesty: EU failing Syrian refugees
Amnesty Secretary General Salil Shetty called upon EU leaders to open their borders, provide safe passage to those seeking refuge, and refrain from "unlawful push-back operations" currently being employed to stop refugees entering the continent.
Only 10 EU member states offered resettlement or humanitarian admission places to refugees from Syria, according to the report. Of the 12,000 places offered, 10,000 have been pledged by Germany. France has offered 500 places and Spain 30.
Eighteen EU member states - including the UK and Italy - have pledged no places, said the UK-based charity.
Amnesty claims that the low chance of being granted asylum is forcing refugees to risk their life by undertaking dangerous boat and land crossings.
The report claims that those who make it to Europe are often mistreated.
Also on Friday, troops loyal to President Bashar al-Assad launched a broad offensive on Friday aimed at expelling rebels from the town of Adra, northeast of Damascus, the state-run SANA news agency reported.
The UK-based Syrian Observatory for Human Rights, an anti-government rights group, also confirmed these reports and documented the names of 19 civilians killed over the past two days adding that the civilians were minority Alawite and Druze.
Syrian Minister of Social Affairs Kinda Shammat described on Friday what happened in Adra as a "massacre".
Shammat told Syrian TV that the army was now carrying out an operation in the area, an industrial section of the town.
The ongoing conflict, which has killed an estimated 126,000 people and driven millions from their homes, was sparked when the government of President Bashar al-Assad launched a crackdown after a series of protests in March 2011.