The attacker struck a large group of mourners at the funeral for the wife of an anti-Taliban militia member in a village just outside Peshawar, capital of Khyber Pakhtunkhwa province, scene of a spate of militant violence lately, the state-run Associated Press of Pakistan.
The BBC and The New York Times, quoting officials and authorities, said the blast killed at least 34 people. The Times said the blast also injured 45, many of them critically.
A police official told the APP the death toll was expected to go much higher "as it was a huge blast amongst the gathering of the mourners."
CNN put the death toll at 37 and reported the Taliban had claimed responsibility for the attack.
A police official told CNN the funeral was for the wife of Muhammad Ejaz Khan, a member of a pro-government militia group.
"We will keep continuing such attacks on all those who support U.S. and the Pakistan military," CNN quoted a Taliban spokesman as saying.
The BBC said many anti-Taliban militiamen were attending the funeral.
On Tuesday, an explosives-laden car bomb rammed into a natural gas station, killing at least 25 people and injuring dozens more in Faisalabad, Pakistan's third largest city in Punjab province. The blast, claimed by the Taliban, occurred near the office of Pakistan's main spy agency.
In a separate incident Wednesday, a truck carrying several people hit a landmine in Dera Bugti district in Balochistan province, leaving four people dead and 18 others wounded, the APP reported.