The suicide bomber who blew herself up outside the Sri Lankan prime minister's office today was a member of the deadliest wing of Tamil Tiger separatists, senior police officials said.

The woman--the latest prominent female assassin in south Asia--killed herself and 12 others after police became suspicious and questioned her outside the office of Prime Minister Sirimavo Bandaranaike. It was not clear if the bomber's target was the 82-year-old prime minister, who works from home but was due in today.

In a nearby Tamil neighborhood two hours later, gunmen on motorcycles shot pro-rebel Tamil politician Kumar Ponnambalam in the head and killed him as he drove his car. Neither police nor party officials would comment on a possible motive.

The explosion came three weeks after another woman blew herself up at an election rally, leaving President Chandrika Bandaranaike Kumaratunga, the prime minister's daughter, with a serious eye injury.

Police identified the woman in today's attack as a member of the Black Tigers, a group they characterized as the deadliest among the Tamil Tigers, a rebel group that has waged a 17-year civil war for independence in northern Sri Lanka. Promotional leaflets and the Tamil Tigers' Web site describe the Black Tigers as a "major wing" of the Tamil Tigers' fighting formations and the women commandos as "Birds of Freedom."

Women have been responsible for some of the region's most notorious assassinations, including that of former Indian prime minister Rajiv Gandhi in 1991 and Sri Lankan President Ranasinghe Premadasa in 1993. The Tamil Tigers have denied involvement in those killings.

About half the Tamil Tigers are women. Senior police officials say they idolize the charismatic rebel group leader, Velupillai Prabhakaran.

Anti-terrorist officers say women are chosen for suicide missions because they do not face the same stringent body searches at checkpoints as men. While there are some female Sri Lankan security officers, there are not enough to post them at all vulnerable places. As a result, women are more frequently asked for an identity card, while men are frisked.