KARACHI, Pakistan—Militants stormed Karachi's Jinnah International Airport late Sunday, exchanging fire with security forces and leaving at least 23 people dead, officials said.

Separately, gunmen and suicide bombers attacked pilgrims from the minority Shiite sect of Islam in the west of the country, killing at least 23 pilgrims.

The Pakistani Taliban, a group closely linked to al Qaeda and its militant allies, claimed responsibility for the airport attack. No responsibility was immediately claimed or assigned for the attack on the pilgrims, but the Pakistani Taliban frequently targets Shiites, who make up about 20% of Pakistan's population.

At the airport, the assault began at around 10:20 p.m. local time and lasted six hours, with gunfire, explosions and a raging fire. The provincial chief minister, Qaim Ali Shah, said 13 airport employees and security personnel altogether were killed by the militants. In addition, 10 militants were killed, he said.

"They attacked the airport security personnel and then entered," Adnan, a witness, said.