Responsibility for the Kabul attacks, which included rockets fired at the five-star Serena Hotel, was claimed by an Afghan Taliban faction led by Siraj Haqqani, who uses his base in North Waziristan, along the Afghan border, to organize an insurgency against American and NATO forces.

Image Secretary of State Hillary Rodham Clinton with Anne W. Patterson, the American ambassador, Wednesday in Islamabad. Credit... Asad Zaidi/Bloomberg News

“This is a very dark day for the U.N. in Afghanistan,” said Kai Eide, the United Nations special representative to Afghanistan. He said officials of the organization would review “whether other appropriate measures need to be taken to protect all our staff.”

No one claimed responsibility for the Peshawar bombing, but the authorities said it appeared to be another in a series of attacks by Pakistani Taliban militants to answer the military’s offensive against their stronghold in South Waziristan.

Since the military moved into the region this month, the Pakistani Taliban have shifted their attacks from suicide bombings aimed at security installations and Western targets to more powerful and more indiscriminate bombings in urban centers intended to kill large numbers of Pakistani civilians.

“The militants want to destabilize the government and intimidate the public,” Mehmood Shah, a retired brigadier and defense analyst based in Peshawar, told the Geo news network. As long as the military operation continues, he added, “We can expect such attacks to carry on.”

A senior intelligence official blamed Taliban militants based in Darra Adamkhel for the attack. “We had an intercept last week that spoke of a ‘heart-rending’ attack in Peshawar,” the official said, requesting he not be identified. The militants, he said, spoke of carrying out the attack to “unnerve” the government. “This explains why they are now targeting civilians,” he said.