Pakistan has lodged a strong protest with the United States-led coalition forces in Afghanistan over the recent firing from across the border that left eight people dead in North Waziristan.

"We have lodged a protest with the Coalition Forces as they are responsible for security on the other side of the [Pakistan-Afghan] border," Foreign Office Spokesperson Tasneem Aslam said on Monday.

Reports said helicopters attacked a residential compound in Saidgi area near the Pakistan-Afghan border.

The spokesperson said the Americans have denied their troops were involved in the attack.

"We have initiated an inquiry; we know fire came from across the border but we don't know who is involved," she added.

Pakistan was also investigating reports that a helicopter had landed on the Pakistani side of the border and then took off.