ISLAMABAD -- At least 35 people were killed and over 200 others sustained injuries on Sunday after a blast ripped through a political rally in Pakistan's Bajaur district, an official of the northwestern Khyber Pakhtunkhwa province told Xinhua.

The official from the governor's office in the provincial capital Peshawar said that local authorities had confirmed that 35 people lost their lives, fearing that the death toll might further rise as at least 50 of the injured are in critical condition.

The official said that the governor has advised all the authorities concerned to provide the best available treatment to the wounded and, if needed, they should arrange for airlifting them to other cities, including Peshawar and the capital Islamabad.

Nasir Mehmood Satti, an official at the Regional Police Office of Malakand division, told the media that the attack took place when a convention of political workers of the Jamiat Ulema-e-Islam-Fazl (JUI-F) was being held near Shanday Mor area on the Munda Khar road of Bajaur.

The police officer said soon after the blast, police, security forces and rescue teams rushed to the site, started a rescue operation, and shifted bodies and the injured to nearby hospitals.

An eyewitness Akbar, who attended the event, told local media that he heard a big blast and saw bodies, the injured and blood.

"I joined other locals to shift bodies and the injured to the hospital. This is a great cruelty on innocent people," said Akbar, while appealing to the public to rush to the hospital for blood donations.

According to the police, it was a bomb blast, and the bomb disposal squad is working to find out whether it was conducted with a planted device or it was a suicide attack.

Pakistani Prime Minister Shahbaz Sharif condemned the attack and expressed grief over the losses of lives.

No group has claimed responsibility for the blast yet.