Missiles hit a religious school in a village just inside Pakistan's border with Afghanistan on Monday, killing six people, officials and state media said.
There was no claim of responsibility, but the incident follows a series of strikes from unmanned U.S. aircraft in recent months against militant leaders holed up in Pakistan's wild tribal belt.
It occurred hours before U.S. President George W. Bush receives Pakistan's prime minister at the White House amid mounting American international pressure on Islamabad to act against Taliban and al-Qaida strongholds on its territory.
According to state-run Pakistan Television, the missiles came down in Azam Warsak, a village in the South Waziristan region. It said six people were killed and several others injured.
PTV didn't identify the source of its information or provide any other details.
Two Pakistani intelligence officials told The Associated Press that the missiles hit an Islamic school in the village.
One of the officials, who is based in Tank, a town near South Waziristan, said initial reports indicated that the six dead included three children and three adults.
He said militants, including foreigners, were active in the area, but he didn't know if they had been in the school at the time.
Both officials asked for anonymity because they were not authorized to speak publicly.
The Pakistan army spokesman was not available for comment.
Pakistan's border regions have seen a series of missile strikes, apparently carried out by U.S. warplanes. One killed a senior al-Qaida leader in the North Waziristan region in January.
The incidents have strained relations with Washington, particularly since a new Pakistani government took power nearly four months ago and sidelined stalwart U.S. ally President Pervez Musharraf.
The government is seeking peace agreements in its mountainous border region in an attempt to curb Islamic extremists blamed for a wave of bloody suicide attacks across Pakistan last year.
NATO claims that the resultant cease-fires are contributing to escalating violence in Afghanistan, while U.S. officials warn that al-Qaida leaders could be plotting another 9/11-style attack on the West.
Pakistani Prime Minister Yousuf Raza Gilani, who meets Bush and other senior officials in Washington on Monday, insisted in the past week that his government would use force only as a last resort.