The last of Syria’s declared chemical weapons have been shipped from the war-torn country and are en route for destruction at sea.

The last of Syria's declared chemical weapons have been shipped from the war-torn country and are en route for destruction at sea, the world's chemical weapons watchdog said on Monday.

"As we speak, the ship (carrying the last chemicals) has just left the port (of Latakia)," Ahmet Uzumcu, head of the Organization for the Prohibition of Chemical Weapons, said at a press conference in The Hague.

"Removing the stockpile of precursor and other chemicals has been a fundamental condition in the program to eliminate Syria's chemical weapons program," Uzumcu said.

Syria had previously shipped out 92 percent of its stockpile of chemical weapons under the terms of a UN-backed and US-Russia brokered agreement last year.

But the remaining eight percent of the stockpile remained at one site and Damascus and is scheduled to transport the most dangerous materials to an American ship because of security concerns.

A Danish ship is now to take the chemicals to the US ship Cape Ray for destruction at sea, while some chemicals are to be destroyed at sites in Finland, the US and Britain.

"We hope to conclude soon the clarification of certain aspects of the Syrian declaration and commence the destruction of certain structures that were used as chemical weapons production facilities," Uzumcu said.

Under last year's agreement Syria had until the end of June for the destruction of its chemical weapons, but it has been widely acknowledged that the deadline would not be met.

The deal was reached after a sarin nerve gas attack in an armed groups-held Damascus suburb killed around 1,400 people. Damascus agreed to hand over its chemical arsenal.