ISLAMABAD - A suicide bomber targeted a large gathering of Shiite Muslims in the capital of Pakistani-controlled Kashmir yesterday, killing five people and wounding 80, a rare sectarian attack in an area police said has little history of terror-related violence.

Muslim militants have fought for decades to free Kashmir, which is split between India and Pakistan and claimed by both, from New Delhi's rule. But while Muzaffarabad, the capital, has served as a base for anti-India insurgents to train and launch attacks, the city - and most of the Pakistani side - has largely been spared any violence, as militants have focused their firepower across the frontier in the Indian-controlled portion, police officer Sardar Ilyas said.

Yesterday, the suicide bomber detonated his explosives as police tried to search him at a checkpoint outside a commemoration of the seventh-century death of Muhammad's grandson. The gathering attracted about 1,000 people, said police officer Tahir Qayum. The five killed included two police, he said.

Most of the 80 injured were Shiites participating in the tribute, held every year during the Islamic holy month of Muharram, Ilyas said. Ten of the wounded were in critical condition, he said. Minority Shiites in Pakistan are often targeted by radical Sunnis.

During another Shiite gathering in the southern port city of Karachi, an explosion wounded 30 people, but authorities determined that the blast was caused by gas that had accumulated in a sewer line, Police Chief Waseem Ahmad said. Shiites later protested on the road where the blast occurred, and torched three vehicles, he said.

The bombing in Muzaffarabad highlights the growing extremism of militants in Pakistani Kashmir. Many of the armed groups in the region were started with support from Islamabad. But some have turned against their former patrons and joined forces with the Taliban because the government, under U.S. pressure, has reduced its support.

The partnership is a dangerous development for Pakistan because it could enable the Taliban to carry out attacks more easily outside its sanctuary in the country's tribal areas in the northwest. More than 500 people have been killed in retaliatory attacks since mid-October, when the military launched a major offensive against the Taliban tober in the militant stronghold of South Waziristan near the Afghan border.

In one such revenge attack, three bombs planted in the house of Sarbraz Saddiqi, a government official in Kurram tribal region, exploded yesterday, killing him, his wife and five children, police officer Naeemullah Khan said. Three others were wounded.

The Pakistani government has pledged to persevere in its battle against the militants despite rising violence, but political turmoil threatens to distract the government as calls have multiplied for President Asif Ali Zardari and other senior ruling party officials to resign following a recent Supreme Court decision to strike down an amnesty protecting them from corruption charges.

Zardari lashed out at his opponents yesterday during his first public appearance since the court ruling a week and a half ago, accusing them of threatening Pakistan's democratic system and "colluding" with extremists attacking the state.

"It is a conspiracy to weaken Pakistan," Zardari said in a speech marking the second anniversary of the bombing death of his wife, former Prime Minister Benazir Bhutto.

The amnesty was issued by former President Pervez Musharraf as part of a U.S.-backed deal to allow Bhutto to return from self-imposed exile in 2007. After her death, Zardari led the ruling Pakistan People's Party to victory in 2008.