The head of the world's chemical weapons watchdog called Wednesday for temporary ceasefires in Syria's raging civil war in order to meet tight disarmament deadlines.

"I think if some temporary ceasefires can be established, I think those targets could be reached," Organisation for the Prohibition of Chemical Weapons chief Ahmet Uzumcu told journalists in The Hague.

The OPCW has been charged with dismantling Syria's chemical arsenal and facilities by mid-2014 under the terms of a UN Security Council resolution drawn up after deadly nerve gas attacks in August.

Uzumcu said during a rare public briefing on the state of Syria's disarmament that the timeline "is extremely tight".

He denied however that the deadlines, including the destruction of all production facilities by 1 November, were unrealistic.

"Much depends on the situation on the ground, that's why we have urged all parties in Syria to be cooperative," Uzumcu said.

"The elimination is in the interest of all."

The OPCW said on Tuesday it was sending a second wave of inspectors to bolster the disarmament mission in the war-ravaged nation.

Uzumcu said that another 12 experts were being sent to Damascus.

Syria has won rare international praise for its cooperation with the chemical disarmament mission, deployed in Damascus since 1 October.

"The cooperation with Syria has been quite constructive. The Syrian authorities are cooperative," said Uzumcu.

Inspectors have already visited one chemical site in Syria and are visiting another on Wednesday, with some weapons already destroyed.

"There are 20 sites to be visited in the coming weeks," Uzumcu said.

Speaking at the same press conference, Uzumcu's political advisor Malik Ellahi said "at the moment there are certain sites that are located in areas which are dangerous."

He told AFP afterwards: "Ceasefires are very important."

Ellahi added that most sites to be inspected at this stage were in Syrian government-controlled areas.

"You can't treat security as a static concern. It's a dynamic and fluid situation. That's why we work very closely with the United Nations."

"For any particular move that the team has to undertake, the security situation is assessed. Unless we get the clearance from our UN colleagues, we don't move."

Because of the nature of its work, the OPCW rarely communicates in detail about its activities.

It is currently holding a regular closed meeting of its 41-member Executive Council, during which Uzumcu discussed progress in Syria.

Some 19 OPCW arms experts and 16 UN logistics and security personnel are in Syria and have started to destroy weapons production facilities, with footage of their work broadcast on Syrian television.

UN chief Ban Ki-moon has warned that the weapons inspectors face unprecedented danger, saying it would take 100 foreign experts to complete "an operation the likes of which, quite simply, has never been tried before".

The mission will have bases in Damascus and Cyprus.

Syria has already made a declaration of its weapons facilities, and the UN resolution set a November 1 deadline for the eradication of production and chemical mixing facilities.

The Russian-US-inked disarmament document agreed on by the OPCW and the UN says that inspectors in Syria can take the unusual step of visiting suspect sites not mentioned by Syria in its inventory.

But Uzumcu said that so far no country had requested that an undeclared site be visited.

"We are at the beginning of a difficult process and there are significant challenges. Nevertheless our organisation is well equipped in terms of knowledge expertise and experience to fulfil this mandate," he said.