COLOMBO (AFP) - A Tamil Tiger suicide bomber on a motorcycle blew himself up outside a police station in northern Sri Lanka on Monday, killing at least 12 and wounding 40 others, officials said. The powerful blast occurred during the morning rush hour directly in front of the police building in the tightly-guarded town of Vavuniya, 258 kilometres north of the capital Colombo, the defence ministry said. The wounded, some of them schoolchildren, were rushed to the main hospital where 23 people including 19 police were admitted for further treatment, doctors said. "It was a Tiger suicide bomber who rammed his (explosives-packed) motorcycle as policemen were leaving for duty," military spokesman Udaya Nanayakkara said. "All those killed in the attack were police personnel," police spokesman Ranjith Gunasekara said, identifying the victims as nine policemen and three female constables. The most senior police official was not in the building at the time of the blast, a policeman in Vavuniya said when contacted by telephone. Vavuniya is a de facto frontier town bordering territory further north held by the rebels, who are fighting for a separate Tamil homeland in the majority Sinhalese island. The drawn-out conflict has claimed tens of thousands of lives. The latest attack came as the defence ministry reported that 47 rebels and eight security personnel were killed in weekend battles in the north. The latest deaths raise the number of rebels killed by security forces to 4,269 since January, according to the defence ministry, which says 386 security personnel and police have died in combat during the same period. The government insists it now has the upper hand in the 36-year-old conflict with the Tigers, and has poured a record 1.5 billion dollars into the war effort this year. In other clashes, air force fighter jets pounded a "logistics base and combat vehicle conversion plant" in Mullaitivu district, further north of Vavuniya, on Sunday, the defence ministry said. However, the rebel Liberation Tigers of Tamil Eelam (LTTE) said Sri Lankan jets had killed two civilians and wounded 11 more in the Sunday morning attack. In the island's eastern district of Batticaloa, suspected Tiger gunmen shot dead two police constables while a trooper from the paramilitary home guard unit was shot dead elsewhere in the region on Sunday, the ministry said. It said troops also killed four more Tiger rebels in a fresh confrontation in the north on Sunday. There had been no reaction from the Tigers to the ground battles or the latest attack in Vavuniya.