London, Oct 15 (IANS): Fighting is preventing access to chemical sites in some rebel-held areas in Syria and short-term cease-fires can help UN-appointed chemical arms inspectors to work, according official.

"Chemical experts had already reached five out of at least 20 facilities capable of producing chemical weapons," Ahmet Uzumcu, Director-General of the Organisation for the Prohibition of Chemical Weapons (OPCW), told the BBC in an interview Monday.

However, routes to some of the sites went through opposition-held territory and this prevented access, Uzumcu said.

He added that one abandoned site is located in a rebel-held area, and that his team is hoping to access it. Uzumcu called for local, short-term ceasefires to allow experts to work.

Syrian officials have been cooperating and facilitating the experts' work, he added.

According to a UN resolution, Syria's chemical weapons production equipment must be destroyed by Nov 1 and stockpiles must be disposed of by mid-2014.

The OPCW was established in 1997 to monitor and destroy chemical weapons across the world.