Eleven people were killed near Peshawar in a roadside bombing of a prison van, authorities said. In addition to policemen and prisoners, the dead included four schoolchildren traveling in a passing bus, authorities said.

Peshawar is the capital of Pakistan's Northwest Frontier Province, where al-Qaida and Taliban militants reportedly have bases.

Earlier, a suicide bomber in Islamabad rammed a car loaded with explosives into the country's Anti-Terrorist Squad headquarters, located in a police compound, injuring 10, the Press Trust of India reported.

Officials said they found a letter at the blast site warning such attacks would continue if Pakistan doesn't stop supporting the war on terror, the news agency said.

The attacks came as lawmakers were gathering in parliament for a rare closed-door intelligence briefing on the rising threat of Islamist militancy.

The attacks followed the Sept. 20 bombing of Islamabad's Marriott Hotel, described as the biggest explosion in Pakistan's history, which killed more than 50 people and injured hundreds.