International peacekeepers in Kabul have received credible reports that they could be targeted by car bombs or kidnapped by Taliban and Al Qaeda remnants in a bid to force the release of prisoners, authorities said Monday.

Intelligence reports indicate as many as six vehicles were being rigged with booby-traps which would be detonated near peacekeeper security patrols, according to Flight Lt. Tony Marshall, a spokesman for the security force in Kabul.

"Surveillance had made us aware of where these vehicles were being kept and what the intentions were of these groups,'' he said.

The peacekeeping force has already advised journalists and Western aid groups that they were at risk of being kidnapped in Kabul and elsewhere following the recently concluded Operation Anaconda, which targeted Al Qaeda and Taliban units in eastern Afghanistan.

On Monday, Marshall said the kidnap threat extended to peacekeepers.

Marshall said the intelligence information indicated that peacekeepers and others may be kidnapped by extremist groups ``to either promote their particular cause or achieve some end goal, be it the release of prisoners'' held by the United States and anti-Taliban Afghan forces.

The kidnap threats have been received over the last several weeks, and peacekeepers have adapted their security measures as a result, he said.

He said the warnings were credible and ``significant,'' and that they covered the entire 18-nation, 4,500-strong force, which is responsible for helping the interim government secure the capital.

He wouldn't say how many Al Qaeda or Taliban remnants are believed to be in Kabul or its environs.

``We know there are small groups of Al Qaeda moving around within the country, possibly there are one or two in or around the outskirts of Kabul,'' he said.

So far, peacekeepers have been involved in only three major shooting incidents since deploying in late December. In general the situation in the capital remains relatively calm.