UN Secretary-General Ban Ki- moon and the head of a joint mission in charge of ridding Syria of chemical weapons, Sigrid Kaag, on Wednesday welcomed the reports that a shipment of the country's stockpile of sulphur mustard, commonly known as "mustard gas," has left the territory of the Middle East country, a UN spokesman told reporters here.

The shipment was confirmed by the Joint Mission of the Organization for the Prohibition of Chemical Weapons (OPCW) and the United Nations. Kaag, the special coordinator of the joint mission, "welcomed this shipment as an important step in the elimination of the Syrian Arab Republic's chemical weapons programme," UN spokesman Martin Nesirky said at a daily news briefing here. "The secretary-general welcomes the news of this latest shipment."

"The Joint Mission looks forward to Syria's continued efforts to complete the removal of the remaining chemical materials in a safe, secure and timely manner, through systematic, predictable and high-volume movements," said the spokesman.

The Joint Mission also encouraged Syria to maintain momentum in implementing the relevant resolution of the UN Security Council and the decisions of the OPCW Executive Council to rid the country of its chemical weapons program.

According to the plan approved by the OPCW, Syria's chemical weapons will be transported outside its territory to ensure their destruction in the "safest and soonest manner" and no later than June 30.

In early January, Kaag told the 15-nation council that although the Joint Mission's operation has been delayed, it is expected to meet its June deadline.

The Joint Mission was set up in October 2013 to oversee the elimination of Syria's chemical weapons under relevant Security Council resolution.

Syria renounced its chemical weapons material and joined 1992 Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons under an agreement brokered by Russia and the United States last year.