ISLAMABAD—A suicide bomber struck a Shiite Muslim mosque outside the Pakistani capital April 5 killing 22 people, the latest sign of rising sectarian violence and the growing reach of the Islamic insurgency.

The attack took place in the city of Chakwal, about 100 km south of Islamabad. It came less than 24 hours after at least eight paramilitary troops were killed in a bombing in the capital and six days after militants stormed a Police academy in the eastern city of Lahore.

Violence in Pakistan has long since spilled out of the tribal areas along the Afghan border where Taliban and Al-Qaeda militants find a haven, and into Pakistan's heartland. The bombing was the third major attack in six weeks in Punjab, the country's most populous and affluent province.

A Taliban-linked group claimed responsibility for the April 5 bombing, which occurred at the entrance to a Shiite mosque packed with worshipers. Insurgents in Pakistan have stepped up efforts to sow chaos by fomenting violence between Sunni Muslims and the country's Shiite minority.

District Police Officer B. A. Nasir said guards intercepted the bomber before he could enter the mosque compound where at least 1,000 people were gathered, thus preventing even greater carnage.

U.S. President Obama has pledged massive new development aid to Pakistan, and said authorities must take decisive steps to quell the insurgency. The militants' increasing strength in Pakistan has greatly complicated Western troops' battle with the Taliban and allied groups in Afghanistan.

The “Fedayeen al-Islam”, which is believed to be either allied with Pakistan's Taliban movement or a front for another Taliban-linked group, claimed responsibility for the mosque attack in calls to Western news agencies. The claim could not immediately be substantiated.

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