At least 25 people were killed and around 35 others were injured in the restive Balochistan province, when a powerful blast hit a convoy of the deputy chairman of Pakistan's Senate, Abdul Ghafoor Haideri.
The bomb blast occurred near the town of Mastung, 50 km from the provincial capital of Quetta, on Friday, after prayer time.
ISIS claimed responsibility for the attack, reports quoting official sources said.
The Amag news agency, an ISIS outfit, said a bomber wearing an explosive vest carried out the attack, which was condemned by a former local ISIS affiliate.
Reports said, the convoy of Abdul Ghafoor Haideri was exiting a seminary when the bomb exploded.
Haideri, a member of Jamiat Ulema Islam, a right-wing Sunni Islamist political party that is part of Prime Minister Nawaz Sharif's coalition government, sustained minor injuries in the attack, while his driver was killed.
"I am alive, Allah has saved my life. It was all very sudden. Broken pieces of the windscreen hit me. I am injured but safe," Haideri told a local TV station on phone.
Ghazanfar Ali Shah, a police official, said the convoy appeared to have been hit by a suicide bomber.
Eyewitnesses told TV channels that sustained firing followed the bombing. "When the firing stopped, we saw bodies everywhere," said Salahuddin, a seminary student.
Television footage showed a vehicle mangled by the blast. Several other vehicles on the spot were also damaged.
Emergency was declared at hospitals in Mastung and Quetta.
Dr Sher Ahmed, the district health chief in Mastung, said at least 25 people died and another 37 were injured, adding that the condition of 8 to 10 among the injured, who were hit by pellets and shrapnel, was also critical.
JUI-F chief Maulana Fazulr Rehman has condemned the attack and said that it was not the first on the party. "A number of our companions have been martyred in this attack, but we have to continue to work for this country and Islam," he said.