Five people, including a doctor, were killed when their ambulance was hit by a Claymore mine in northern Sri Lanka [Images] on Wednesday, a pro-Tamil Tiger website said.

The explosion ripped through the vehicle inside an area held by the Liberation Tigers of Tamil Eelam, Tamilnet.com said.

It said government forces had infiltrated the area to carry out the attack. "A doctor, his wife, two nurses and the driver of the ambulance belonging to Nedunkerni hospital, were killed, when the Deep Penetration Unit of the Sri Lanka army attacked the ambulance," the article said.

Military officials said they were not aware of the blast inside rebel-held territory.

The blast followed a car bomb attack in Colombo targeting a government Tamil politician who escaped with injuries. However, three people were killed in that attack.