Health officials in Pakistan say 39 people have been killed and more than 120 others wounded in an explosion at a political rally.

No one has claimed responsibility for the blast, which police suspect was a suicide bombing.

The explosion occurred on Sunday at the gathering of an Islamic party in a town bordering Afghanistan in the northwestern province of Khyber Pakhtunkhwa.

Police say over 400 people were present at the time of the explosion.

Footage from a local hospital shows injured people being taken there one after another even though the interior was already crowded.

Political parties are stepping up their campaign to appeal to voters as the term of the lower house of the national parliament expires in August.

The risk of terrorism tends to grow during election campaigning in Pakistan. In 2007, a suicide bomb attack killed former Prime Minister Benazir Bhutto, who was an opposition leader at the time.