Pakistan has summoned the US ambassador and protested a cross-border raid which killed at least 15 people in a village near Afghanistan, officials said on Thursday.
"The US ambassador in Pakistan was summoned to the foreign ministry on Wednesday and a very strong protest was conveyed to her," foreign ministry spokesman Mohammad Sadiq told AFP.
"The ambassador said that she would convey it to her government."
Pakistan officials said at least 15 people were killed in the raid by Afghan-based international forces on Wednesday.
The Pakistan army has also lodged a protest with the US Office of the Defence Representative in Pakistan (ODRP).
A military spokesman said "we reserve the right of self defence and retaliation to protect our citizens and soldiers against aggression."
On Wednesday, both the US-led coalition and separate NATO-led security force in Afghanistan said they had no knowledge of the incident, which reportedly took place in Pakistan's South Waziristan.
The remote tribal area has become a haven for Al-Qaeda and Taliban fighters who are accused of attacking troops in Afghanistan.
An official in South Waziristan, Mowaz Khan, said that helicopters dropped troops into the border village of Jalal Khel, and that the soldiers shot civilians who had left their homes upon hearing the choppers.
He said 15 people including women and children were killed in the raid.