Pakistani officials said on Saturday that al-Zawahiri was not at the site attacked and regretted the loss of civilian lives.
"The US ambassador will be called to the foreign office," Shaikh Rashid Ahmed, the information minister, said, adding that a protest would be lodged over the attack on Friday in
which, according to residents, 18 civilians were killed and three homes destroyed.
Another senior Pakistani government official said Osama bin Ladin's deputy was not in Damadola village, near the Afghan border, at the time of the attack.
Ahmed said: "We want to assure the people we will not allow such an incident to reoccur," reading a statement which termed the attack as "highly condemnable".High-level figures?
CNN quoted sources saying the CIA ordered Friday's strike after receiving intelligence information that al-Zawahiri was in a village near the border.
ABC News quoted Pakistani military sources as saying that five of those killed were "high-level" al-Qaida figures.
But tribesmen in Damadola village in the Bajur tribal area said only locals were killed - 18 of their kinfolk, including eight women and five children.
The FBI anticipates performing DNA tests on the victims, a law enforcement official said on Saturday.
"The US ambassador will be called to the foreign office... We want to assure the people we will not allow such an incident to reoccur"
Shaikh Rashid Ahmed,
In Washington, Pentagon, State Department, National Security Council and intelligence officials did not immediately provide additional details about the attack.
DNA tests to determine the victims' identities are expected to be conducted in the US, according to the law enforcement official who spoke on condition of anonymity because a formal request for such testing had not been made public.
Up to 11 extremists were believed to be among the dead, according to unidentified Pakistani officials quoted in news reports.
However, survivors of the attack in Damadola denied that fighters were there. A Pakistani intelligence officer told the AP that some bodies were taken away for DNA tests.
Haroon Rashid, the area's National Assembly representative, was quoted by the Afghan Islamic Press news agency as saying: "I know all the 18 people killed. There was neither al-Zawahri nor any other Arab among them. Rather they were all poor people of the area."
US sources said it would not be known whether al-Zawahiri was killed until the remains of the dead were examined.
But US sources familiar with the operation cast doubt on Pakistani claims that al-Zawahri was not among the dead, saying it was too early to determine his fate.
The sources, who spoke only on condition of anonymity because of the issue's sensitive nature, said the air strike believed to have been conducted by CIA-operated unmanned drones armed with missiles, was carried out on the basis of "very good" intelligence indicating that the al-Qaida official was at the targeted location.
However, Al-Arabiya satellite television said on Saturday al-Zawahri was alive, quoting a source it said has contact with al-Qaida.
"Reports of his death are wishful thinking," it quoted unidentified sources as saying.
Two senior Pakistani officials said on Saturday that the CIA had acted on incorrect information and al-Zawahiri was not at the site of the attack.
"Their information was wrong, and our investigations conclude that they acted on a false information," said a senior intelligence official who has direct knowledge of Pakistan's investigations into the attacks.
His account was confirmed by a senior government official, who said al-Zawahiri "was not there".
A Pakistani intelligence source said he had been told by US officials the strike was ordered based on information that al-Zawahiri and Mullah Mohammad Omar, the ousted Taliban leader, had been invited to a dinner to celebrate this week's Muslim Eid al-Adha festival.
They had no confirmation, however, that either had been there at the time of the attack at about 3am on Friday (2200 GMT Thursday).
The hit was said to be carried out
by unmanned drones (file)
Mullah Dadullah, a senior Taliban commander, said no Taliban commander had been at the dinner.
Another intelligence official said four US aircraft had fired four missiles that destroyed three houses in the attack.
Major Chris Karns, a spokesman at US Central Command in Florida, the command responsible for the region, said there had been no official report of an attack in Pakistan.
As well as the 18 villagers killed, five other bodies were thought to have been removed after the attack and Pakistani agents were uncertain where they had been taken, said the first intelligence source, who declined to be identified.
One Damadola resident said three or four foreigners had come from Afghanistan for Eid. Another said he had seen bodies of at least two people who seemed to have been outsiders.
"Where these bodies have gone, I don't know," he said.
Pakistan's The News newspaper said the villagers had been buried after a mass funeral led by Maulana Faqir Muhammad, a cleric wanted for giving shelter to suspected al-Qaida members.
Ahmad Zaidan, Aljazeera's Pakistan bureau chief, said US forces had targeted Pakistani tribal areas in the past week, hitting a house in the tribal Mirah Shah area, killing eight Pakistani civilians and drawing a protest from Pakistan's Foreign Ministry.
Zaidan also reported that thousands of people had demonstrated in the area against the US air strike on Saturday.
Pakistani police tear-gassed tribesmen who burned down a US-funded aid agency office on Saturday.
Tribesmen stand by their home
damaged by Friday's air raid
An estimated 5000 people had gathered at a stadium near Khar, the main town in the Bajur tribal zone.
Some demonstrators set fire to the offices of Associated Development Construction, a non-governmental organisation funded by the US Agency for International Development, an official at the aid group said.
"They have attacked our office in reaction to the deaths on Friday and put it on fire. It is badly damaged," Fazal Maibood, a site engineer, said.
Cement bags stolen
The mob also stole hundreds of bags of cement, and up to 20
tonnes of steel construction material were damaged by the fire, he added.
Police later fired tear gas shells to disperse the mob after the crowd headed towards a music and video cassette market, while security forces fired two shots in the air.
Security men were also seen arresting young tribesmen and
bundling them into the backs of vans.
Aljazeera's Zaidan said Pakistani Muslim organisations had called for protests on Sunday against the US presence and violations in the country.