Weapons inspectors have begun work with Syrian officials on securing the Assad regime's chemical arsenal, taking the first steps towards destruction of the weapons next year.

The Organisation for the Prohibition of Chemical Weapons (OPCW) said a team of about 20 inspectors had completed a first day of work in Syria on Thursday.

"Joint work with the Syrian authorities has begun on securing the sites where the team will operate, especially in outlying areas," a web bulletin said. "The team has also been considering the health and environmental hazards which they may have to confront. In addition, planning continues for one of the team's immediate tasks, disabling Syria's chemical weapons production facilities, which should begin soon. Discussions on the size of Syria's stockpiles are also under way, as well as long-term planning, so that deadlines unanimously imposed by the executive council of the OPCW and the UN security council are met."

The OPCW executive council has set a 1 November deadline for the destruction of chemical weapons production. The destruction of the entire Syrian arsenal, estimated by western intelligence at 1,000 tonnes of sarin nerve agent and other poison gases, has to be completed by mid-2014, according to the OPCW decision backed unanimously by the UN security council last Friday.

OPCW officials had predicted that the first few days in Syria would be spent going through paperwork on the country's declaration of its chemical weapons stockpile to ensure it included all the relevant information, and to make plans with Syrian officials to visit the production plants and munitions. The announcement that work had already started on locking down those sites suggests that the process could be ahead of schedule.

The weapons inspectors believe some of the sites they will have to visit will be close to the front lines in the Syria's civil war. Other visits will involve crossing rebel-held territory, and will require UN staff negotiating safe passage with the opposition. OPCW officials are concerned about the health effects of wearing chemical protection suits together with body armour, possibly with air tanks, in the 35C heat at some of the sites.

In its statement, The Hague-based organisation said: "In their discussions with the authorities, the OPCW-UN team was keen to stress that the onus was on the Syrian government to meet the verification and destruction deadlines. It was however reiterated that the joint mission will provide the necessary technical support to meet these obligations. Meeting the regular reporting requirements will be one indication of compliance."