Volunteers carry a blast victim on a stretcher at a hospital in Quetta on September 29, 2023, after a suicide bombing in Mastung district. AFP
While the celebration of the Prophet's birthday is accepted by the majority of Islamic sects in Pakistan, certain denominations view it as an unwarranted innovation.
"A procession of hundreds of people came out of the Madina mosque and as it reached Al Falah road a suicide bomber targeted it," said Abdul Razzaq Sasoli, deputy commissioner of Mastung district.
"At least 25 people were killed and more than 80 injured -- including 20 critically," Zubair Jamali, home minister of Balochistan, told AFP.
Jan Achakzai, Balochistan's minister for information appealed urgently for blood donors to help treat the wounded.
He also announced a three-day mourning period.
Every year mosques and government buildings are elaborately illuminated with strings of lights, and people come march in processions to mark the Prophet's birthday.
On the same occasion in April 2006, a suicide bomber killed at least 50 people in the port city of Karachi after detonating a device at a gathering of Sunni Muslims.
No group ever claimed responsibility for the attack, although three men from the banned sectarian Lashkar-e-Jhangvi group were indicted.
Balochistan, Pakistan's least populous province, is also home to several militant groups fighting for independence or a greater share of the region's mineral resources.
Pakistan's Taliban, which has stepped up attacks against military and government targets since the return to power of the Taliban in Afghanistan in August 2021, said it had nothing to do with Friday's Balochistan attack.
"The Tehreek-e-Taliban Pakistan (TTP) asserts no connection to this attack, and our stance on bombings in public spaces is unequivocal," the group said in a statement.
The regional chapter of the Islamic State group, known as Islamic State-Khorasan (IS-K), has also carried out attacks in the area in the past.
"The attack on innocent people who came to participate in the procession... is a very heinous act," the interior ministry said in a statement.
Separately, Pakistan's military said Friday four soldiers had been killed as they fought an attempt by TTP militants to infiltrate Balochistan from Afghanistan.
"During fire exchange, 3 x terrorists were also sent to hell," it said in a statement.