Three children and two women were killed when missiles fired by a suspected unmanned US aircraft hit a village on the Pakistan-Afghanistan border in the third such attack in as many days, officials said.
They said the strike on Friday destroyed two houses belonging to tribesmen in North Waziristan's Goorweck Baipali village, right on the border with Afghanistan.
Residents said two pilotless aircraft fired three missiles. Pakistan's army, however, denied any strike was carried out on its sovereign territory.
A tribesman in nearby Miranshah said the village straddled the border between Pakistan and Afghanistan.
An interior ministry official earlier said locals reported the strike was on the Pakistani side of the border but later it was clarified that the houses damaged in the strike were on the Afghan side.
In a separate attack a day earlier, at least five militants were killed when a missile fired from an unmanned plane hit a house in the North Waziristan village of Mohammad Khel, officials said.
The White House declined to comment directly on the claim of US involvement from across the border in Afghanistan in recent days.
"We respect their sovereignty and we support their new civilian government," spokeswoman Dana Perino said of Pakistan, adding that US president George W Bush "grieves any time there is a loss of innocent life".
The latest strike follows Pakistani accusations that US-led forces based in Afghanistan killed 15 people in a border village on Wednesday in neighbouring South Waziristan district.
Both the US-led coalition and the separate NATO-led security force operating in Afghanistan have said they have no knowledge of that incident.
South Waziristan is a known haven for Taliban and al-Qaeda militants. Several officials said the missile strike killed children and women, not militants.