ISLAMABAD, Pakistan -- The death toll from the suicide attack at a political gathering in the Bajaur district of Pakistan's northwest Khyber Pakhtunkhwa province on Sunday jumped to 54 after more injured succumbed to their injuries, a police official said on Monday.  Additional Inspector General of Police Shaukat Abbas told the media that 10 of the injured lost their lives since Monday morning during their treatment in different hospitals of the province.  "At least 12 of the deceased are below 12 years of age. The medics feared that the death toll might further rise," said the officer, adding that over 80 injured are undergoing medical treatment.  The police officer also said the initial investigation revealed that the Khorasan chapter of the Islamic State was involved in the attack.  Earlier on Sunday, Nasir Mehmood Satti, the Regional Police Office of Malakand division under which Bajaur lies, told the media that the attack took place when a suicide bomber exploded his jacket at the workers' convention of the Jamiat Ulema-e-Islam-Fazl (JUI-F) at the Munda Khar road of the district. Inspector General of Police of the province Akhtar Hayat Khan told the media on Monday that the initial investigation revealed that over 10-12 kg of explosives, along with ball bearings, were used in the suicide blast. Pakistani President Arif Alvi and Prime Minister Shahbaz Sharif condemned the attack, expressed deep grief over the losses of lives, and extended heartfelt sympathies to the bereaved families. No group has claimed responsibility for the attack yet.