The death toll from a suicide bombing at an election rally in Pakistan has risen to 128, a government official said.

Provincial caretaker home minister Agha Umar Bungalzai said about 300 people were also wounded on Friday when the bomber targeted a rally for candidate Siraj Raisani, who was running for a seat in the provincial legislature.

The attack took place in Mastung, a town in the south-western Baluchistan province.

The attack was the deadliest yet ahead of the July 25 parliamentary election and it came despite assurance from the military that it would take all possible measures to ensure a peaceful environment for the vote.

The Islamic State group has claimed responsibility for the attack.

The group gave no reason for the bombing that killed Siraj Raisani, who was running for the election on the Baluchistan Awami Party ticket.

Raisani was attending a rally in Mastung, a town in Baluchistan, when the suicide bomber targeted him.

Pakistan PoliticsPeople hold an injured supporter of former prime minister Nawaz Sharif after a clash with police in Lahore (K.M. Chaudary/AP)

The violence came as disgraced former prime minister Nawaz Sharif returned to Pakistan.
Mr Sharif has returned with his daughter Mariam to face a 10-year prison sentence on corruption charges, anti-corruption officials said.

Mariam Sharif faces seven years in jail.

Pakistan PoliticsPolice use force to disperse supporters of former prime minister Nawaz Sharif, who gathered to see him in Lahore (K.M. Chaudary/AP)

The suicide bombing was the second election-related violence to take place on Friday.

The first bomb killed four people when it exploded in the north-west, near the election rally of a senior politician from an Islamist party who is running for parliament from the town of Bannu.

The explosion targeted candidate Akram Khan Durrani, who escaped unhurt, police said.

Mr Durrani is running against popular former MP Imran Khan. He is a candidate of Muttahida Majlis-e-Amal, an election alliance of radical religious groups.

Mr Khan, who hopes to become the next prime minister, condemned Friday’s attack against his opponent, Mr Durrani.

In a tweet, he said there seems to be a conspiracy to sabotage the vote. But he said the people of Pakistan will not allow anything to prevent “historic” elections from taking place.