At least 40 people were killed in an explosion at a political gathering in Pakistan's northwestern Khyber Pakhtunkhwa province on Sunday, Geo News reported, citing local officials.

The report did not mention a possible cause for the blast that took place at a gathering of the conservative Jamiat Ulema Islam-Fazl (JUI-F) party, known for its links to hardline political Islam, in the former tribal area of Bajaur.

Bilal Faizi a spokesman for Rescue 1122, a first-responder service in the province, told Reuters that 17 had been killed according to initial reports, but over 70 were injured and the toll could rise.

Pakistan has seen a resurgence of attacks by Islamist militants since last year when a ceasefire between the Tehreek-e-Taliban Pakistan (TTP) and Islamabad broke down.

The TTP pledges allegiance to, but is not directly a part of, Afghanistan's Taliban.