The second US drone attack in as many days killed 10 people in northwest Pakistan on Sunday, intelligence officials said, an incident likely to raise tensions in the standoff between Washington and Islamabad over NATO supply routes to Afghanistan.
The remotely-piloted aircraft fired four missiles at a suspected Islamist militant hideout in the Birmal area of the South Waziristan tribal region near the Afghanistan border, officials said.
A drone strike in the same area killed two suspected militants on Saturday.
The United States and Pakistan are locked in difficult negotiations to re-open overland supply routes to NATO forces in Afghanistan, with no signs of a breakthrough.
Islamabad blocked the routes last November to protest the death of 24 Pakistani soldiers by cross-border friendly fire from NATO aircraft. The supply lines through Pakistan are considered vital to the planned withdrawal of most foreign combat troops from Afghanistan before the end of 2014.
The CIA drone campaign fuels anti-US sentiment in Pakistan and is counterproductive because of collateral damage, Pakistani officials say. But US officials say such strikes are highly effective against militants.