The morning bomb blast in Rawalpindi, a few hundred yards from the Pakistani army's headquarters, was followed by another suicide bomb attack at a highway checkpoint outside the eastern city of Lahore that injured at least 15 people. There was no immediate claim of responsibility for either attack.

The attacks followed a surge in extremist violence that swept across Pakistan last month and coincided with the government's long-awaited military operation to crush the Taliban in the group's stronghold in rugged, largely lawless South Waziristan. Nearly 300 people have been killed in those attacks.

The violence led the United Nations to announce yesterday that it was suspending long-term development efforts in the country's northwest and pulling out some of its non-Pakistani staff members.

Pakistani military commanders say the offensive in South Waziristan continues to make significant progress as it hems in Taliban and Uzbek extremists from three directions.

An army spokesman, Maj. Gen. Athar Abbas, said yesterday that 12 extremists had been killed in the previous 24 hours, while troops recovered five truckloads of extremist arms and explosives and destroyed two sites where roadside bombs were being made.

But with no end to the battle in South Waziristan in sight, extremists' retaliatory strikes on major Pakistani cities have taken a devastating toll on everyday life in the Muslim nation of 180 million. Many private schools in Islamabad, the capital, have been shuttered for two weeks while administrators struggle to shore up security at their buildings.

Last week, the northwestern city of Peshawar was rocked by a car-bomb blast at a market that killed 118 people and injured at least 200. The attack occurred at a bazaar filled with women's fabric stores and cosmetics shops, and many of the dead and injured were women and children.

"Our forces are fighting to get rid of the terrorists, whether it's in Waziristan or Islamabad," Information Minister Qamar Zaman Kaira said yesterday at a news conference. "This is not a small group, and these are not simple criminals. But we are fighting them."

Extremists have broadened their array of targets in recent weeks. Schools were shut down last month after two suicide bombers attacked a college in Islamabad, killing six people. Last week's attack on the women's bazaar in Peshawar was preceded Oct. 9 by a suicide car-bomb blast at a bustling market in the same city that killed 53.

The target yesterday appeared to be the active and retired military officials who line up each month at a branch of the National Bank of Pakistan to pick up their pension checks and wages. The bomber drove up on a motorcycle and detonated explosives while people waited in line, said Rao Iqbal, deputy police inspector general. There were at least 80 people standing outside the bank when the blast occurred, witnesses said.

The indiscriminate nature of the attacks was cited by the United Nations as a key reason for suspending its long-term aid work in northwestern Pakistan. Eleven U.N. staff members have been killed in attacks this year. The latest occurred Oct. 5, when a suicide bomber hit the World Food Program office in Islamabad and killed five U.N. workers.

The United Nations will reduce the level of international staff in Pakistan and confine its work to emergency, humanitarian relief, and security operations, and "any other essential operations as advised by the secretary-general," the organization said in a statement. Staff that remain will be assigned additional security.