Britain's elite force SAS is waging a "secret war" in Iraq that has led to more than 3,500 insurgents being "taken off the streets of Baghdad," a news report has said.

"We took over 3,500 terrorists off the streets of Baghdad in around 18 months," a senior British officer was quoted as saying by The Sunday Telegraph newspaper.

The British daily disclosed that hundreds of terrorists have been killed by the SAS, waging a "secret war" against al-Qaida in Iraq.

It said that while the majority of the terrorists were captured, several hundred, who were mainly members of the "al-Qaida in Iraq" have been killed by the SAS, which is part of a highly secretive unit called "Task Force Black".

The SAS had played a key part in defeating a network of car bombers in Baghdad that had brought devastation to the capital.

The "Task Force Black" has nearly broken the back of the terrorist network and reduced bombings in Baghdad from about 150 a month to just two, the report said.