ISLAMABAD, PAKISTAN — American ground troops carried out a rare raid on Pakistani soil Wednesday, a cross-border attack from Afghanistan that left up to 20 people dead and provoked sharp condemnation from Pakistan's government.
The raid, described by Pakistani officials as having been carried out by helicopter-borne commandos in a hamlet just on the Pakistani side of the frontier, is likely to inflame tensions at a time when Islamic militants are already threatening to attack Pakistani officials and installations in retaliation for recent strikes against them by government forces.
The incursion into Pakistan's tribal areas by U.S. troops in Afghanistan was highly unusual, though not unprecedented. A similar raid by helicopter took place in 2006. American forces are widely believed to have conducted missile strikes targeting senior Al Qaeda figures in Pakistan, but other types of incursions are rare.
In Afghanistan, the NATO-led International Security Assistance Force and the separate U.S.-led military coalition, which conducts most operations in the border zone, refused to comment on the raid in South Waziristan, a known militant stronghold.
Pakistan's Foreign Ministry, in a sharply worded statement, did not specifically blame American troops for the early morning strike. However, it said it had summoned U.S. Ambassador Anne W. Patterson to lodge a formal protest.
The Foreign Ministry called the raid a "grave provocation" and a violation of Pakistani sovereignty.
"Such actions . . . certainly do not help our joint efforts to fight terrorism," the statement said. "On the contrary, they undermine the very basis of cooperation, and may fuel the fire of hatred and violence that we are trying to extinguish."
Pakistani officials offered varying accounts of the strike that triggered the Pakistani protests. But local, provincial and central government officials all insisted that the raid, which began about 3 a.m., involved foreign troops who crossed over from Afghanistan.
The governor of the North-West Frontier Province, which has partial authority in the tribal areas, said that as many as 20 people died, including women and children. Gov. Owais Ahmed Ghani termed the strike "outrageous."
An army spokesman, Maj. Murad Khan, said that about 15 people were killed, including seven civilians. Later, though, the chief army spokesman, Maj. Gen. Athar Abbas, told Dawn television that seven deaths had been confirmed.
Local authorities put the initial death toll at 17, but said some people were missing or gravely injured.
A witness in the district, which is called Angoor Adda, said people in the village of Musa Nika awoke to the sound of explosions. Foreign troops then fired on residents, he said, and three helicopters could be seen afterward flying back toward Afghanistan.
Pakistani news reports cited military and intelligence officials as saying the incursion came after a group of Taliban fighters crossed into Afghanistan and attacked Afghan and Western troops. The coalition forces then pursued the militants back across the border, the officials said.
North Atlantic Treaty Organization and U.S. forces have claimed the right of "hot pursuit" in the event of an ongoing attack. But Pakistan has often said it has not authorized foreign troops to chase militants who flee into its territory.
U.S. Special Forces have entered Pakistan on occasion. The elite SEAL Team 6 raided a suspected Al Qaeda compound at Damadola in 2006.
With their own battle casualties rising in Afghanistan, the United States and other Western governments have been demanding that Pakistan do more to rein in Islamic militants operating from its side of the border. In recent weeks, the Pentagon has seen an intensified debate over whether to send troops into what the U.S. regards as a militant haven.
Both the Pentagon and U.S. Central Command refused to comment on Wednesday's raid.
The strike came just three days before Asif Ali Zardari, the head of the Pakistan People's Party, is seeking the presidency in a vote by Pakistani lawmakers.
Zardari, who took over the party leadership when his wife, Benazir Bhutto, was assassinated Dec. 27, appears poised to win easily in the contest to replace President Pervez Musharraf, who stepped down last month rather than face impeachment. But Zardari is widely perceived as being pro-American, an unpopular stance in Pakistan these days.
After months of waffling, the government, now led by Zardari's party, has moved forcefully against militants in the last few weeks, killing hundreds in the Bajaur tribal area.
Pakistani troops also have taken the offensive in the restive Swat valley, where officials said 25 insurgents were killed in fighting Wednesday.
The government is highly sensitive to the perilous security situation. Wednesday's raid came the same day shots were fired at the motorcade of Prime Minister Yusaf Raza Gillani; he was not in the procession, which was headed for the airport near Islamabad, the capital, to pick him up, and no one was hurt. Insurgents were blamed for the attack.
Special correspondent Zaidi reported from Islamabad and Times staff writer King from Istanbul, Turkey. Special correspondent Zulfiqar Ali in Peshawar, Pakistan, and Times staff writer Julian E. Barnes in Washington contributed to this report.