Senior Pakistani militant leader Mullah Nazir has been killed by a US drone strike, security officials say.
He died with at least five fighters when two missiles struck his vehicle in the north-west tribal district of South Waziristan, they said.
He was the leader of one of four major militant factions in Pakistan, accused of sending fighters to back the Afghan Taliban and fight foreign troops there.
Mullah Nazir is one of the most high-profile insurgents killed by drones.
He had survived a suicide bomb attack blamed on rival militants in November.
Wednesday night's drone strike targeted him as he and his fighters prepared to swap to a new vehicle after his pick-up developed a fault, reports said.
It took place in Angoor Adda, near South Waziristan's main town of Wana, close to the Afghan border.
Reports say Mullah Nazir's deputy, Ratta Khan, was also killed in the attack.
Officials also said four militants were killed in a separate attack in North Waziristan, but their identities are not known.
Presidential approval?
Local residents were quoted as saying that they heard on mosque loudspeakers announcements that Mullah Nazir was dead. Funeral prayers were said for him later on Thursday.
Mullah Nazir's group is one of several militant factions operating in Pakistan's restive north-west - in recent years there have been divisions among these groups.
Analysts say Mullah Nazir had formed an alliance with the government and opposed the Pakistani Taliban, with whom he was at odds because he favoured attacking US forces in Afghanistan rather than Pakistani soldiers.
After November's attack on him, his faction told a rival group led by Taliban leader Hakimullah Mehsud, to leave the Wana area.
Reports say he was also seen as an enemy of militants from the Islamic Movement of Uzbekistan (IMU), and praised by Pakistan for expelling Uzbek and other foreign fighters from Pakistan in 2007.
His death could be a contentious issue between Washington and Islamabad, they add, because the Pakistani military views commanders like him as key to keeping the peace internally.
However, the Americans will point to the killing as a vindication of their controversial drone programme, says the BBC's Aleem Maqbool in Islamabad.
For years, he was a key figure involved in supplying fighters and support to the Afghan insurgency, our correspondent says.
Drone strikes have increased in frequency since US President Barack Obama took office in 2009. Hundreds of people have been killed, stoking public anger in Pakistan.
The dead include senior al-Qaeda and Taliban leaders, as well as an unknown number of other militants and civilians.
The US does not normally comment on individual drone operations, but last year it emerged in the New York Times that the US president personally approved or vetoed each drone strike.
Islamabad has called for an end to the attacks saying they violate the country's sovereignty, but analysts say Pakistan has privately sanctioned such actions in the past.
