Pakistani officials said four rockets or shells were apparently fired by the US military while fighting suspected militants in Afghanistan's eastern Khost province late on Saturday.
The fire hit the nomads' tent at Bangi Dar, in Pakistan's North Waziristan tribal area.
At least four children were also wounded in the incident.
The officials - one an intelligence official, the other a local government administrator - spoke on condition of anonymity.
There was no immediate confirmation from the Pakistan government or military.
In Kabul, Lieutenant Mike Cody, a spokesman for the US military in Afghanistan, said that a security post along the border in Khost was attacked from the Pakistani side at 4pm on Saturday, and the US military, coordinating with the Pakistani military, used artillery to return fire at the point of attack.
Cody said there were no reports of casualties on either side. The intelligence official confirmed that a coalition post had been fired at.
About 20,000 US troops are in Afghanistan since the Taliban government was overthrown in 2001.
Fire from coalition forces has sometimes landed in Pakistani territory.
Pakistan is a key ally in the US-led "war on terrorism" but does not allow US troops to operate on its side of the rugged and ill-defined border where foreign fighters are believed to be hiding.
Last month, Pakistan protested to the US military in Afghanistan over two air attacks, one on a village in North Waziristan that killed eight people, and the second, a missile strike that hit a village in Bajur tribal region where al-Qaida figures were believed to be meeting.
Thirteen civilians and, according to Pakistan, five foreign fighters, including one al-Qaida operative on the US most-wanted list, died.