At least 30 people have been killed in US missile strikes in the South Waziristan region of Pakistan.
Pakistani intelligence officials described all those killed as insurgents.
The US military does not, as a rule, confirm drone attacks, but its armed forces operating in Afghanistan are the only forces that deploy drones in the region.
The drones struck as hundreds of people gathered for a funeral in a region controlled by militant chief Baitullah Mehsud.
With the mountainous area on the Afghan border out of reach of government forces, security officials and Taliban militants have been giving widely differing death tolls, with some saying up to 65 people were killed.
The first strike by an unmanned drone killed at least six in Shubi Khel, a remote area about 65km north of the main district town of Wana.
As mourners gathered for funeral prayers, another drone fired three more missiles into the crowd, officials and residents said.
Pakistan officially objects to the strikes by pilotless US aircraft.
The attack came as the Pakistani army is preparing an offensive against Baitullah Mehsud.
The military went on the offensive against Taliban fighters allied with Mr Mehsud in the Swat Valley, northwest of Islamabad, in May and are in the final phase of that operation.
The army has no information on the attack on the funeral in the remote area under Mr Mehsud's control.
Mr Mehsud, an al-Qaeda ally accused of plotting the assassination of former prime minister Benazir Bhutto in 2007, had been in the area but was not reported hurt.
The US has offered a reward for information leading to Mr Mehsud's location or arrest.