Pakistan's army says it has confirmed that coalition forces in Afghanistan launched a deadly missile strike into Pakistan's tribal region earlier this week.

An army spokesman, Major General Athar Abbas, said Friday an unmanned coalition aircraft fired the missiles on a house in Damadola village in Pakistan's northwestern Bajaur region Wednesday. He said 14 people were killed in the attack.

The spokesman said Pakistan has lodged a formal protest against the strike with coalition forces deployed in Afghanistan. Both NATO and the United States lead coalition forces in the neighboring country.

Earlier Friday, officials in Bajaur said they found the body of a Pakistani soldier in the tribal region. They said a letter left on the body said the soldier had been killed in revenge for Wednesday's attack. The letter was signed by the militant group Tehrik-e-Taliban. Maulvi Omar, a spokesman for the militant group, had vowed on Thursday to avenge the suspected U.S. missile strike.

Locals frequently allege that American pilotless drones carry out such strikes, but Pakistan officially bars foreign military operations within its territory.

Meanwhile, Islamist parties in Pakistan are condemning Wednesday's suspected missile strike as a violation of the country's sovereignty.

The attack comes as militants are negotiating a peace deal with the new Pakistani government.

Some information for this report was provided by AFP and AP.