ISLAMABAD, Pakistan - A car bombing that killed at least six people and wounded dozens near the Danish Embassy yesterday raised fears that al-Qaeda-linked extremists might be moving to fill a void left by other Islamist fighters seeking truces with Pakistan's new government.

The powerful blast occurred in a leafy, upscale neighborhood of the capital, just outside the gates of the embassy, which has been the target of angry protests over caricatures of the prophet Muhammad published in Danish newspapers.

It was the second bombing in less than three months to target foreigners or foreign interests in the capital.

The explosion, heard across much of the normally tranquil city, shattered windows in the embassy building, left a deep crater in the road outside, and wrecked dozens of vehicles nearby.

Most embassy personnel were no longer working in the building after protests early this year, when Danish newspapers reprinted the 2005 cartoons. The dead included two policemen, a janitor at the Danish mission, and passersby, authorities said.

The force of the blast, which occurred during the lunch hour, twisted the embassy's heavy metal gates and knocked down a section of the wall surrounding the building.

Ayman al-Zawahiri, the second-in-command of al-Qaeda, recently had urged followers to strike at Danish targets because of the cartoons. The blast, coming after weeks of relative calm in Pakistan, suggested that the government may be vulnerable to such attacks even if it can make peace with local Taliban members.

Pakistan's ruling coalition, led by the party of assassinated former Prime Minister Benazir Bhutto, condemned the attack. But officials said they would not be deterred from talks with Islamic extremists based in Pakistan's tribal areas along the Afghan border and elsewhere in the country's volatile northwest.

Those negotiations have resulted in accords with some smaller groups but not with Baitullah Mehsud, the leader of the main umbrella group of Pakistani Taliban. Pakistani authorities and the CIA have blamed Mehsud, who is thought to have links to al-Qaeda, for masterminding the Dec. 27 assassination of Bhutto, an accusation he denies.

Until now, groups such as Mehsud's have cited the policies of the Pakistani government as a pretext for carrying out attacks. Yesterday's bombing suggested wider Western interests could be targeted.

U.S. officials have been giving the recently elected leadership time to establish control over Pakistan, even as it makes overtures to extremist groups in tribal regions. Privately, Defense Department officials acknowledge disagreement over whether to press the government to move more aggressively against al-Qaeda-linked fighters.

The U.S. Embassy urged American nationals to exercise caution when moving about in the capital after yesterday's blast, which damaged two nearby diplomatic residences. The area is heavily guarded and most motorists need diplomatic plates to enter.

The force of the explosion was so strong that the engine of the car in which the bomb was believed to have been planted was flung more than 100 feet. The nearby office of a United Nations-funded group was evacuated, and more than 30 of its employees suffered cuts from flying glass.

Diplomatic missions in Islamabad have been sensitive to threats against them. The Dutch mission moved into a heavily guarded five-star hotel earlier this year. In Copenhagen, Prime Minister Anders Fogh Rasmussen called the bombing "an attack against Denmark" and said his nation "would not be cowed by terrorists."

The last major attack targeting foreigners occurred March 15, when an explosion at a restaurant killed one person and wounded a dozen, including five FBI employees.