ISLAMABAD - The Pakistani Taliban claimed responsibility yesterday for the devastating bombing of a religious procession in Karachi - a rare attack in Pakistan's commercial hub and a sign the militants may be escalating their war against the state.

Monday's bombing, which killed 44 people in the heart of the southern port city, underscored the group's ability to strike far from its sanctuary in the northwest and its determination to hit back at a government that has launched a military campaign against it.

Attacking Karachi "means they're trying to expand their frontiers of terrorism," said retired general and military analyst Talat Masood.

Although the teeming city of about 15 million has often been the scene of sectarian, ethnic and political violence, the Pakistani Taliban have rarely claimed any attacks there. Many analysts believe the group has spared it in the past because its militants used the city as a haven to raise money and to rest.

But yesterday, the group announced it was behind the bombing of minority Shiite Muslims marking the holy day of Ashoura as they marched through the heart of Karachi.