At least 46 people were killed in a suicide bombing at a political gathering of a leading Islamic party in northwest Pakistan's Khyber Pakhtunkhwa Province on Sunday, local media reported. 

The death toll may rise further as over 130 people were injured in the blast.

The blast took place at a gathering of the conservative Jamiat Ulema Islam-Fazl (JUI-F) party in Bajaur district, which borders Afghanistan.

An emergency has been declared in the hospitals of Bajaur and adjoining areas where most of the injured were taken, said district police officer Nazir Khan. The critically injured were transported from Bajaur to hospitals in the provincial capital Peshawar by military helicopters.

The provincial police chief Akhtar Hayat said the explosion was caused by a suicide bomb. According to local media reports, around 500 people were present at the site.

The targeted party, the JUI-F, is a major ally of Prime Minister Shehbaz Sharif's coalition government, which is preparing for national elections to be held by November.

Sharif condemned the blast, calling it an attack on the democratic process of Pakistan. He vowed that those responsible would be punished.

No one has yet claimed responsibility for the attack.

(With input from agencies)