United Nations: The al-Qaeda terror network may attempt a biological or chemical terrorist attack in "just a matter of time", according to an unpublished United Nations (UN) report.

Some members of the al-Qaeda terror network are likely to possess portable surface-to-air missiles and may use them to target military transport planes.

The threats were among several findings detailed in a report by the al-Qaeda and Taliban Sanctions Committee of the United Nations. It also cited a shifting of the terror network's strategy, towards "softer" targets probably based on a biological or chemical attack, CNN reported quoting the report.

Heraldo Munoz, the Chilean Ambassador to the United Nations and head of the sanctions committee, said the panel believes it's "just a matter of time" before al-Qaeda attempts a biological or chemical terrorist attack.

"The only restraint they are facing is the technical complexity to operate them properly and effectively," he said. "All I can say at this point is al-Qaeda and some of the associates have tried to get hold of chemical and biological weapons."

However, the killings and detentions of several members of al-Qaeda have damaged the terror network, Munoz said.

PTI