An Afghan policeman searches a vehicle at a security checkpoint. Picture: Sayed Mominzadah/Xinhua

Kabul - At least 15 people were killed when a bomb exploded on Saturday at a campaign rally in the northern Afghan province of Takhar, officials said.

At least 33 others were wounded in the incident in Rostaq district, said provincial council member Mawlawi Keramatullah and the head of the district hospital, Nazir Mohammad Nabil.

Another provincial council member, Azam Afzali, put the casualty figures at 21 dead and at least 50 wounded.

The bomb was placed in a motorbike and exploded as the candidate for parliament, Nazifa Yousufi Bieg, was preparing to deliver a speech to her supporters. She survived the attack, according to Afzali.

No group immediately claimed responsibility. However, the Taliban has vowed to do anything to sabotage the parliamentary election set for October 20.

This is the third such attack to have taken place in recent days.

On Tuesday, a suicide bombing at an election rally in southern Helmand province left at least eight dead and 11 others wounded.