Pakistan stepped up security at all military installations after twin suicide blasts at its largest arms factory killed 67 people, highlighting the growing extremist threat in the Muslim world's only nuclear-armed nation. Police said Friday they arrested a third suspected bomber not far from scene. They also recovered a suicide jacket from a nearby mosque and seized explosives. The terrorist attack, one of the worst-ever in Pakistan, adds to turmoil from political squabbling that is threatening to tear apart the ruling coalition now that Pervez Musharraf has quit as president. The two main parties - traditional rivals who united to force him from power - were preparing for a make-or-break meeting Friday that could see the party of Prime Minister Nawaz Sharif, the second largest, quit. He is demanding all judges fired by the one-time military ruler be quickly reinstated, something the Pakistan People's Party, the largest bloc in Parliament, has not yet agreed to. The two sides also diverge on who should succeed Musharraf as president and whether he should face trial. One of the biggest challenges for the five-month-old government, however, will be tackling extremist violence. The twin suicide bombings Thursday - claimed by the Taliban as a response to army attacks on militants in the volatile northwest - underscored the determination by insurgents regardless of who is in power. More than 400 people have died in 20 suicide bombings in the last three months. The death toll from Thursday's blasts in Wah, a city 35 kilometers west of the capital Islamabad, was steadily climbing. Police and factory officials put it at 67 on Friday, with at least 102 people wounded. The carnage could have been worse, however, with authorities saying they arrested a man they believe would have been a third bomber. "The army and police arrested a suspected bomber not far away from scene of the attack," said local police official Mohammed Saeed. "They also recovered a suicide jacket from a nearby mosque and seized explosives." It was unclear whether the suspected would-be bomber was found with the explosives or why he apparently failed in his mission. The attacks were a blow to Pakistan's military, which is fighting militants in troubled Bajur tribal region near Afghanistan, where Taliban, al-Qaida and local Islamic militants are believed to be hiding. The fighting there has displaced more than 250,000 residents. Hours after the attack, an umbrella group of Taliban militants claimed responsibility, saying it was to avenge the army's air strikes in Bajur. "The army has killed hundreds of innocent people, and we attacked it to teach it a lesson," said Maulvi Umar, a spokesman for Pakistani Taliban groups, threatening more violence unless the military ceased its operations. Musharraf resigned Monday to avoid the humiliation of impeachment after nearly nine years in power that began with a bloodless coup. While the former military commander was considered a vital member of Washington's war-on-terrorism coalition, the new civilian government drew US criticism for giving priority to striking peace deals with militants when it came to power. The peace effort was popular with many Pakistanis who are angry over the conflict's toll on civilians. But it has met only limited success, and the government is again pursuing military operations against militants in the rugged region along the Afghan border. Workers were streaming through two gates of the massive weapons complex Thursday during a shift change 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. Nine days earlier, the Taliban had 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 North West Frontier Province bordering.