DERA ISMAIL KHAN, Pakistan — Helicopters ferried foreign troops from Afghanistan in an unusual ground and air attack on a border village that left at least 15 people dead today, including civilians, officials said. Pakistan’s government blamed American or NATO forces and warned that the raid undermined its efforts against terrorism.

In other violence buffeting the country, snipers fired on the prime minister’s limousine and the army said it killed two dozen militants in another part of the militancy-torn northwest.

American officials say Pakistan’s tribal regions along the Afghan border have turned into havens for Al Qaeda and Taliban-linked militants involved in attacks on American and NATO forces in Afghanistan.

The accusations — and suspected American missile strikes — have strained relations between America and Pakistan’s new civilian government in the days before it it elects a successor to ousted President Pervez Musharraf.

Officials gave differing accounts of today’s pre-dawn raid in South Waziristan, part of the tribal belt where officials suspect Osama bin Laden and Al Qaeda No. 2 Ayman al-Zawahri are hiding. It was unclear whether any militant leaders were killed or captured.

Pakistan’s military said ground forces from NATO’s International Security Assistant Force in Afghanistan were ferried to the raid by two helicopters. If true, it would mark an extremely rare crossborder foray by foreign ground troops, although American drone aircraft prowl the rugged border region armed with missiles.

The Foreign Ministry was more vague, saying American-led coalition or NATO troops were responsible for “a grave provocation” and “a gross violation of Pakistan’s territory.”

It said it lodged a strong diplomatic protest over the “immense loss of civilian life.”

“Such actions are counterproductive and certainly do not help our joint efforts to fight terrorism,” it 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.”

A spokesman for the American-led coalition in Afghanistan, 1st Lieutenant Nathan Perry, said it had “no information to give” about the alleged operation, while a spokesman for NATO troops there denied any involvement. The American embassy in Islamabad declined to comment.

The governor of North West Frontier Province, the top administrator for the tribal belt, said up to 20 people died, including women and children.

An Army spokesman, Major Murad Khan, said 15 people died, including seven civilians. He would not say whether the others were suspected militants.

Habib Khan Wazir, who lives in the area, said he heard helicopters, then an exchange of fire.

“Later, I saw 15 bodies inside and outside two homes. They had been shot in the head,” Mr. Wazir told an AP reporter by telephone.

He claimed the dead included women and children and that all were civilians.

“There was darkness at the time when the Americans came and killed our innocent people,” Mr. Wazir said. “We would have not allowed them to go back alive if they had come to our village in daylight.”

Residents said the dead were buried today.

America has pushed Pakistan to crack down on the militancy inside its territory, and there has been debate in Washington over how far America can go with its own strikes.

AP reported last year that American rules of engagement allowed ground forces to go a little over six miles into Pakistan when in hot pursuit and when forces were targeted or fired on by the enemy. American rules allow aircraft to go 10 miles into Pakistan air space.

Pakistani officials say crossborder strikes are a violation of their sovereignty. They plead with American and NATO commanders to share intelligence and allow Pakistani troops to carry out all raids on their territory.

Relations deteriorated further this year when Pakistan said coalition aircraft bombed one of its border posts, killing 11 troops.

The civilian government — under pressure from Washington — has taken a tough line against militants, seeking to persuade a skeptical public that security forces are fighting Islamic extremists for Pakistan’s sake, not Washington’s. But American officials recently accused rogue elements within Pakistan’s premier intelligence agency of sharing sensitive information with militants.

In a mark of the country’s precarious stability, snipers fired on the motorcade for Pakistan’s prime minister today as it drove to the airport to pick him up, striking his car window at least twice, officials said.

Neither Prime Minister Yousuf Raza Gilani nor his staff were in the vehicles.

The attack was the second apparent assassination attempt in Pakistan in quick succession.

Shots were fired last week at a car carrying Lynne Tracy, the top American diplomat in Pakistan’s troubled northwest, as she was headed to her office in the city of Peshawar. No one was hurt in that shooting.

Militants in the northwest have claimed responsibility for a series of suicide attacks, saying they are in revenge for recent military operations in at least three areas of the region.

Murad, the army spokesman, said security forces killed between 25 and 30 militants in an offensive today against militants in the Swat valley, a former tourist destination were Islamic extremists tried to seized control last year.