At least 45 people have been killed in a suicide bombing at an Islamist party rally in north-west Pakistan.

More than 100 people were also injured in the explosion in Bajaur district, where Jamiat Ulema-e-Islam-Fazl (JUI-F) was holding a meeting.

No group has said it carried out the attack, which is being investigated. A motive remains unclear.

Officials have warned the death toll may rise further, as several people are in a critical condition.

The authorities say a rescue operation has been completed and all injured have been taken to hospital.

Security forces have cordoned off the area while the investigation takes place. The police chief of Khyber Pakhtunkhwa confirmed that the explosion was a result of a suicide blast. According to bomb disposal teams, approximately 10kg of explosive material was used in the attack.

Hundreds of people were attending the JUI-F workers' convention on Sunday in the town of Khar, in the tribal district of Bajaur, Khyber Pakhtunkhwa province, near the border with Afghanistan.

Pictures showed hundreds of people gathered under a canopy when the blast happened close to the stage.

One eyewitness said the tent collapsed, trapping people who were desperately trying to escape.

Images broadcast on local TV show ambulances ferrying injured people to hospital, while police confirmed those with serious injuries had been flown by military helicopters to the nearby city of Peshawar for urgent medical treatment.

Authorities have declared a health emergency at the district hospital.

Some badly injured people have been waiting in the hallways of health clinics struggling to cope with the high number of casualties.

A regional leader of the JUI-F, Maulana Ziaullah, was killed in the blast, local officials told the BBC.

JUI-F is a major religious political party and forms part of the government coalition in Pakistan's parliament.

Pakistan's Prime Minister Shehbaz Sharif condemned those responsible as being terrorists who have "targeted those who speak for Islam, the Quran and Pakistan" and said they would face "real punishment".

"The terrorists are enemies of Pakistan, we will eliminate them from the face of existence," the PM said in a statement.

The political gathering was an opportunity for the JUI-F to rally its support, ahead of an election expected to take place later this year.

While no group has yet said they carried out the attack, the local branch of Islamic State group (IS) in Pakistan claimed to be behind several attacks this year in Bajaur and has previously claimed targeting JUI-F.

In June, the militants said they were behind the assassination of a party official in the village of Inayat Killi.

IS issued the claim in the name of its "Khorasan Province" branch (ISKP), which operates in Afghanistan and north-west Pakistan. The group also claims attacks in Pakistan in the name of its "Pakistan Province" branch.

The Pakistani Taliban (TTP) condemned the attack and denied any involvement.

In recent years attacks the TTP and other militant groups have been on the rise again in north-west Pakistan after the Afghan Taliban gained power in neighbouring Afghanistan in 2021. The TTP resumed attacks after ending a ceasefire last November.

Additional reporting by Usman Zahid and Abdirahim Saeed.