Two Pakistani nomad women have been killed after a rocket fired across the border from Afghanistan landed on their tent, Pakistani officials say.
Four children were hurt in the attack late on Saturday in North Waziristan.
Locals say US-led coalition forces in Afghanistan fired four rockets into Pakistan's tribal area after coming under fire from unknown attackers.
A US spokesman confirmed coalition forces had returned fire into Pakistan, but was not aware of casualties.
The incident is the third this year in which civilians have been killed inside Pakistani territory in apparent missile strikes by US-led forces who are hunting al-Qaeda and Taleban suspects in the mountainous border area.
A number of villagers lost their homes in the Bajaur strike
Pakistan complained twice in January to US-led forces after two strikes within a week left at least 26 people dead in North Waziristan and in the Bajaur tribal area.
Pakistan's President Pervez Musharraf said on Saturday that "a close relative" of al-Qaeda number two Ayman al-Zawahiri had been killed in the second of those attacks.
But a number of local villagers also died and there were protests against the US in Pakistan.
In the latest rocket attack, officials say US-led coalition forces fired rockets from the Shankai checkpost in the Afghan province of Khost.
"Two women of a gipsy family were killed and four children were injured when a rocket hit their tent late Saturday," an administration official told the AFP news agency.
He said the children were being treated at a hospital in nearby Mirali district.
US military spokesman Mike Cody said that a security post on the border in Khost had been attacked from the Pakistani side on Saturday afternoon.
"The coalition forces identified this as coming from the border and co-ordinated with the Pakistan military and fired artillery rounds at the point of origin," he told AFP in Kabul.
The US has about 20,000 troops in Afghanistan, but Pakistan does not officially allow them to operate across the border.