At least 12 police personnel, including three women constables, were killed and 23 others injured when a suspected LTTE suicide bomber blew himself up outside a police office in a northern Sri Lankan town on Monday.

The bomber, who came on a motorbike, triggered the explosion in front of the office of Senior Superintendent of Police in the embattled Vavuniya town, officials said.

According to initial reports received from the spot, the blast occurred at around 7.10 am (local time), targeting the police personnel leaving the SSP office for their duties.

The SSP was not at the building at the time of the blast.

Officials blamed the rebel Liberation Tigers of Tamil Eelam for the attack.

Nineteen police personnel and four civilian bystanders were injured and admitted to the general hospital at Vavuniya, hospital sources said.

A school-girl was also among the injured.

Vavuniya borders the rebel-held territory in the restive north, which has witnessed intense battle between the Tamil Tigers and Sri Lankan security forces in recent months.

Monday's blast was the latest in a string of attacks, mostly targeting civilians, by suspected Tamil Tigers since the government scrapped a Norwegian-brokered ceasefire with them in January this year.

At least 23 people, including eight women, were killed and about 90 others injured when roadside bombs ripped through two passenger buses in Moratuwa and Kandy towns on June 6.

Earlier on June 4, at least 27 people were injured when suspected Tiger rebels set off a bomb alongside a packed commuter train in Colombo suburbs.

Another attack on a passenger train on May 26 had left nine people dead and 84 injured in Dehiwala area near the Sri Lankan capital.

Monday's incident also followed a weekend of heavy fighting between the rebels and Sri Lankan troops. The military said Air Force jets destroyed a key LTTE combat logistic facility in a rebel stronghold on Sunday while fierce ground clashes killed 17 Tamil Tigers and two soldiers in the embattled north.