ISLAMABAD, Pakistan—Suicide bombers killed 59 people at a huge arms factory Thursday in one of Pakistan’s deadliest terror attacks, adding to turmoil from political squabbling that is threatening to tear apart the ruling coalition now that Pervez Musharraf has quit as president.

The twin bombings, which also wounded 70 people, hit one of Pakistan’s most sensitive and heavily guarded military installations, underlining the threat posed by Islamic militants to the Muslim world’s only nuclear-armed nation as well as its war-ravaged neighbor, Afghanistan.

Just hours before the blasts, which were claimed by the Pakistani Taliban as a response to army attacks on militants, a key party in the government coalition threatened to quit in a power struggle that has dismayed many Pakistanis and the country’s Western backers.

Workers were streaming through two gates of the sprawling factory complex in Wah, 20 miles west of Islamabad, during a shift change about 2 p.m. when the bombers attacked outside the walls. The force of the explosions knocked many people to the ground and sprayed others with shrapnel.

“I looked back and saw the limbs of my colleagues flying through the air,” said Shahid Bhatti, 29, his clothes soaked in blood.

“It was like a doomsday,” said Ghaffar Hussain, whose nephew was killed. “We are finished, we are ruined,” he said, tears rolling down his face.

Emergency workers with plastic bags on their hands lifted mangled and blackened corpses onto stretchers, while forensic teams picked through scraps of flesh and scattered shoes outside the complex, which employs some 25,000 people making rifles, machine guns, ammunition, grenades and tank and artillery shells.

Tanvir Lodhi of the Pakistan Ordnance Factories said 59 people died. Seventy others were wounded, said Mohammed Azhar, a hospital official.

Nine days earlier, the Taliban declared “open war” on the military over an offensive against militants in the Bajur region. The declaration was issued after a bomb killed 14 people in an air force truck in Peshawar, the main city of the restive frontier along the Afghan border.

Maulvi Umar, a spokesman for Pakistani Taliban groups, told The Associated Press on Thursday that the arms factory attack was to avenge airstrikes on militants in Bajur tribal area, an extremist stronghold in the mountainous frontier region.

More bombings will be carried out in major cities, including the capital and the southern metropolis of Karachi, unless the offensives are halted, he said.

Prime Minister Yousaf Raza Gilani appealed to lawmakers to urgently draw up a national strategy against terrorism “even if you have to sit together for a week.”