Mehsud died near the city of Multan while on his way to a treatment center in Karachi, the sources said.
It was not immediately clear why he was going to the treatment center.
Authorities have been looking into reports that Mehsud died after being wounded last month in a drone attack.
Word of his death contradicts a statement by a Taliban spokesman last week that Mehsud was alive and in hiding.
Also last week, a Pakistani news outlet reported that Mehsud had been killed. State broadcaster PTV reported that Mehsud was wounded in a drone attack this month, died and was buried.
The drone attack occurred at a madrassa, or religious school, said Pakistani intelligence and local officials in North Waziristan. The school had been converted into a training camp for militants, the officials said.
That attack came a few days after Mehsud appeared in a video released by the Pakistani Taliban. In it, he sits next to Humam Khalil Abu-Mulal al-Balawi, the man thought to be the suicide bomber who killed seven CIA officers and consultants and a Jordanian army captain at a base in eastern Afghanistan on December 30.
The Pakistani Taliban claimed responsibility for that attack. It was carried out to avenge the death of Mehsud’s predecessor, Baitullah Mehsud, who died in a suspected U.S. drone strike last year, according to al Qaeda’s commander of operations in Afghanistan, Mustafa Abu Yazid.
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