Zainuddin was a critic of the Pakistan Taliban chief
A tribal leader who opposed the head of the Taliban in Pakistan has been shot dead in the north-western Pakistani town of Dera Ismail Khan, police said.
Qari Zainuddin, 26, who often criticised Taliban head Baitullah Mehsud, was killed by a gunman in his office early on Tuesday.
Separately, reports say six people have been killed in a missile strike by a US drone aircraft in South Waziristan.
They say at least one missile struck a known stronghold of Baitullah Mehsud.
Mehsud's group is blamed for a number of deadly attacks in Pakistan.
Earlier this month, Zainuddin hit out at Mehsud for recent attacks in which civilians have been killed.
The fresh violence comes as the Pakistani army is preparing to launch a new offensive against Taliban fighters under Mehsud's command.
An aide of Zainuddin who was also wounded in the attack that killed the tribal leader said a guard entered the room at Zainuddin's office after morning prayers and opened fire.
"It was definitely Baitullah's man who infiltrated our ranks, and he has done his job," Baz Mohammad told the Associated Press news agency.
Zainuddin was taken to the hospital where doctors pronounced him dead.
'Not a jihad'
Earlier this month, Zainuddin criticised Mehsud after an attack on a mosque which killed 33 people.
He told Associated Press: "Whatever Baitullah Mehsud and his associates are doing in the name of Islam is not a jihad, and in fact it is rioting and terrorism".
"Islam stands for peace, not for terrorism," he had said.
Zainuddin's killing is being seen in Pakistan as a setback for the government in its efforts to isolate Mehsud as the security forces prepare for the next phase of their anti-Taliban offensive in the tribal areas bordering Afghanistan, says the BBC's Mike Wooldridge in Islamabad.
Earlier this month a prominent Muslim cleric who was outspoken in his opposition to the Taliban was killed in a suicide blast at his seminary in Lahore.
Correspondents say Mehsud is thought to head the most powerful group of militants in the country, with a network of alliances with other militants.
His stronghold in South Waziristan, bordering Afghanistan, is an area considered by many to be the hide-out of Osama Bin Laden.