A media outlet with links to Islamic State militants says the group was responsible for a deadly terror attack in Pakistan on Sunday.

At least 45 people were killed after an explosion hit an Islamic party's political rally in a northwestern Pakistani town, near the border with Afghanistan, according to local health authorities. More than 60 others were taken to hospital for treatment.

Pakistani police suspected that it was a suicide bombing.

The Amaq news agency on Monday said a fighter detonated his explosive jacket in the middle of a crowd of party members and senior officials.

It said the attack was conducted in the context of a war against democracy, which suggested the militant group's rejection of Pakistan's political parties and electoral systems.

Political parties are ramping up preparations for elections, as the term of the lower chamber of parliament expires in August. Concerns are growing over the impact the latest terror attack could have on their campaigns and possible subsequent attacks.