Two militants attacked a police station in northwest Pakistan on Saturday, fighting gunbattles before blowing themselves up during a five-hour standoff that killed at least 10 officers, authorities said.

The Pakistani Taliban claimed responsibility for the attack that involved a female suicide bomber, saying it was partly in revenge for the U.S. raid that killed Osama bin Laden.

Similar recent attacks have underscored the vulnerability of Pakistan's security establishment, which is reeling from humiliation following the unilateral U.S. raid.

After the militants entered the police station in Kolachi, TV footage showed black-clad security squads armed with rifles scrambling into positions around the facility. Three explosions rocked the scene in quick succession, setting off plumes of smoke into the sky.

At least 10 police officers died, while five others were wounded during the siege, regional police chief Imtiaz Shah said.

"Our people are being killed inside," said police constable Jan Mohammad, who emerged from the station bleeding after he managed to escape and was quickly taken away by rescue teams.

Intelligence officials said early on that between seven and 20 attackers were involved. But toward the end of the operation, as security teams canvassed the building for leftover bombs or booby traps, police official Salahuddin Khan said investigators believed that only two, possibly three, attackers staged the assault.

Two of them detonated their suicide vests, including the woman, he said. Female suicide bombers are rare, but not unprecedented, in Pakistan. One of the attackers detonated a vest as an armored vehicle tried to enter the compound, police official Javed Khan said.

Pakistani Taliban spokesman Ahsanullah Ahsan said the group sent two attackers, one of them a woman. The group has claimed responsibility for several attacks in the weeks since May 2, when U.S. Navy SEALs killed bin Laden in his compound in the northwest garrison city of Abbottabad.

The Taliban consider Pakistani security forces a legitimate target because of the South Asian nation's alliance with the United States. That relationship that has come under severe strain since the bin Laden raid.

Pakistani leaders say they had no idea bin Laden was hiding in Abbottabad, and have called the U.S. strike as a violation of their sovereignty. U.S. officials say they've seen no evidence top Pakistani leaders knew of the terror chief's whereabouts, but that secrecy was vital to ensuring the mission's success.

The bin Laden raid in particular angered and humiliated Pakistan's military, which was unable to detect the incursion by U.S. choppers.

The embarrassment has deepened as security forces have been unable to stop militant attacks since, including an 18-hour standoff at a naval base in the city's south that killed at least 10 people and bore similarities to Saturday's attack in Kolachi.

Earlier Saturday, 15 insurgents died in the northwest tribal region of Orakzai during a clash between two factions of the Pakistani Taliban, government official Mir Alam said. Orakzai has been the scene of a Pakistani army offensive.

Also Saturday, a small bomb partially went off near a Red Cross office in Karachi, Pakistan's largest city with a population of 18 million. No one was hurt.