The attack happened at a rally of the Awami National Party (ANP), an ethnic Pashtun nationalist party, in the town of Charsadda in troubled North West Frontier Province, they said. The bombing has further raised fears for the security of general elections on February 18, which have already been delayed by the assassination of opposition leader Benazir Bhutto at a rally in December. "According to initial reports 20 people were killed and 25 were injured. One of the injured told me in hospital that it was a suicide attack but I cannot confirm it officially," provincial health minister Syed Kamal Shah told AFP. Interior Minister Hamid Nawaz said the attack was likely carried out by a suicide bomber. "Yes, it was most probably a suicide attack. It was close to the stage but none of the ANP leaders there were hurt," Nawaz told AFP. He said that 14 people were dead and 24 injured. A suicide bombing at a mosque in Charsadda belonging to former interior minister Aftab Sherpao on December 21 killed at least 54 people. Election rallies have been sparse since Bhutto`s death in a suicide bomb and gun attack in Rawalpindi and after the government issued a "security advisory" for candidates to avoid big gatherings. Even the former ruling Pakistan Muslim League-Q party, which backs President Pervez Musharraf, has kept a relatively low profile. Violence blamed on Islamist militants has continued since Bhutto`s death, with attacks and suicide bombings claiming more than 70 lives already this year. Six people were killed in a suicide attack on an army bus in Rawalpindi on Monday. More than 800 people died in similar attacks in 2007, Pakistan`s bloodiest ever year in terms of extremist violence.