KABUL, Afghanistan — In a stark demonstration of insurgents' growing strength on the doorstep of the capital, assailants on Saturday assassinated the governor of neighboring Logar province.

The Taliban claimed responsibility for the attack that killed Abdullah Wardak, a longtime foe of the austere fundamentalist Muslim movement that ruled Pakistan until late 2001 when it was toppled by a U.S.-led invasion.

Wardak's killing was highly symbolic — not only as the settling of long-held grudges by Islamic militants, but as a brazen show of the insurgency's strength in an area a half-hour's drive from Kabul.

Only last month, the governor had delivered news to journalists of the killing of three Western aid workers, together with their Afghan driver, in his province. The women, one of them American, were gunned down, their vehicle riddled with hundreds of bullets as they were returning to Kabul from what was meant to be a short trip south.

Until then, Logar province, just south of the capital, had been regarded as a relatively safe haven for not only foreign aid workers but for government officials like Wardak, a former Cabinet minister under President Hamid Karzai.

Wardak had become uneasy in recent weeks, a member of his entourage said, upon hearing of persistent and escalating death threats by the Taliban. Usually, he shrugged them off.

Official accounts of the fatal attack differed in the hours after it occurred early Saturday. By some accounts, the massive explosion that killed the governor and two bodyguards was a suicide bombing; others said it was triggered by remote control.

A senior police officer in Kabul, Ali Shah Paktiwal, told the Reuters news agency that the attackers were lying in wait when Wardak left his residence.

Wardak had been an active field fighter against the Taliban, commanding a militia that helped overthrow the movement. In their newly emboldened insurgency, Taliban fighters often target officials considered friendly to either the United States or the U.S.-backed government in Kabul. Strikes close to the capital have helped to give at least the impression of encirclement.

Logar province's main airport was forced to close on Friday after a rocket attack. The facility reopened a short time later, officials said.

Across the border in Pakistan, government forces have killed scores of militants in recent days, military officials have said. But in a sign of militants' growing boldness, a municipal building in Peshawar, the main city in Pakistan's restive northwest, was reportedly briefly seized by insurgents.

Pakistan has been roiled by a series of recent American strikes on its soil, including half a dozen airstrikes by what were believed to have been Predator drone aircraft and a ground raid last week by U.S. special forces.

In Afghanistan and Pakistan, strikes targeting local people suspected of aiding Western forces have become more severe in recent months.

Afghan officials said militants in Ghazni province, between the capital and the main southern city of Kandahar, were believed to have beheaded three men on Friday, accusing them of being in league with the Karzai government.