ISLAMABAD, Pakistan-- The government demanded an explanation yesterday for a U.S. airstrike on a remote village near the Afghan border that Pakistani officials said missed al-Qaida's No. 2 leader but killed a number of civilians, including women and children.

Information Minister Sheikh Rashid Ahmed called the attack "highly condemnable," and demonstrations erupted in the border region near the scene of the Friday morning attack. A crowd that gathered at a local market shouted "God Is Great!" and "Down With America!" Protesters ransacked foreign and government aid organizations, damaging computers and setting furniture and motorcycles on fire.

U.S. officials in Washington said Friday that Ayman Zawahri, an Egyptian physician who is Osama bin Laden's lieutenant, was the target of the attack. At least 18 people died in mud-brick homes that were destroyed by the blasts.

A U.S. intelligence official said yesterday that it was "too early to tell" whether Mr. Zawahri was killed or injured, or even if he was present at the time of the attack. But Pakistani officials insisted Mr. Zawahri was not among the dead. The information minister said U.S. Ambassador Ryan Crocker would be summoned by government officials to explain the attack.

A Pakistani intelligence official involved in the hunt for militants in the Pashtun tribal areas along the Afghan border said the U.S. had acted on a false alarm in the Bajur region.

"As per our investigations, Zawahiri was not amongst the dead nor does any evidence suggest his presence in the area," said the intelligence official. "Perhaps U.S. intelligence officials got it all wrong, and in that way, so many innocent civilians died."

A Foreign Ministry statement said a preliminary investigation had found there was "a foreign presence" in the area of the attack, but did not further identify the foreigners. It said that the village was probably targeted from across the border in Afghanistan, and that a government investigation was continuing.

Senior Pakistani military officials said in interviews yesterday that following Friday's attack government officials repeated their insistence to Washington that U.S. forces must not violate the border "in hot pursuit' of suspected militants.

Mr. Zawahri and bin Laden have long been suspected of hiding out in the rugged, tribal areas along the Afghan-Pakistan border.

It was the second time this month that Pakistan's Foreign Ministry complained about a U.S. attack on its territory.

On Monday, the Foreign Ministry lodged what it called a strong protest against an attack by U.S. forces across the Afghan border, which killed eight Pakistanis. Eyewitnesses in that case said U.S. forces in vehicles and helicopters crossed into Pakistan to carry out the attack. Pakistani officials said U.S. troops had not crossed the border, but that the casualties were caused by fire from across the border in Afghanistan, where the U.S. maintains a sizable troop presence.

Such U.S. military operations are politically dangerous for Pakistan's president, Pervez Musharraf, a close ally in Washington's war on terrorism. Islamic parties, which form the main opposition in parliament and govern two provinces on the Afghan border, accuse Mr. Musharraf of being too willing to accommodate the United States. Islamic militants have made several attempts on his life.

Pashtun tribesmen in the remote Bajur region of northwest Pakistan said yesterday that no foreigners were in the area before the attack occurred Friday.

"It is a wild theory that some bodies were taken away from the bombed-out compounds after the attack, which triggered speculation that the dead might include the Egyptian [deputy] leader of al-Qaida," said Anwar Khan, a local tribesman. "It is purportedly true that foreigners were seen in the area in the recent past, but at the moment there are no hideouts of foreigners or Taliban elements in the area."

Security forces used tear gas and fired into the air to disperse the protesters, who ransacked the offices of two foreign-funded non-government organizations, as well as the office of the National Commission on Human Development. They also attacked shops in a market, damaging audio and video equipment and an Internet cafe.

Speaking at the rally, National Assembly member Sahibzada Haroon Rashid said that innocent people had been killed in the attack. He denied that any foreigners, including senior al-Qaida leaders, were in present and that Americans "are responsible for the killing of children and women."