At least 30 people were killed and dozens more wounded after a blast tore through a religious procession in Pakistan's restive Balochistan province on Friday, in what authorities have described as a suicide attack.

The explosion occurred in the Mastung district of the southwestern province, as people were gathering to celebrate the birthday of the Prophet Muhammad, the information minister of the province Jan Achakzai told CNN.

Balochistan, Pakistan's largest province by area, has seen a decades-long insurgency by separatists who demand independence from the country, citing what they say is the state's monopoly and exploitation of the region's mineral resources.

Mastung's Assistant Commissioner, Atta Ul Munim, confirmed to CNN that the explosion was a suicide attack and that 40 people were injured. There has been no claim of responsibility for the explosion.

He claimed a senior police officer, who was killed in the explosion, was the target of the attack.

The critically injured have been transferred to hospitals in Quetta, the province's capital, while others are being treated in a local hospital in Mastung, he said.

Achakzai said the bodies of the victims have also been moved to a hospital but that he expected the number of casualties to rise.

Pakistan's caretaker prime minister Anwar-ul-Haq Kakar strongly condemned the blast in a statement.

"The Prime Minister expressed his condolences to the families of those who died in the blast," a statement from his office said. "Prime Minister's prayers for forgiveness for the deceased and patience for the families."

Police in Karachi, Pakistan's largest city some 600 kilometers (370 miles) from Mastung, have been instructed to tighten security and remain on "high alert" in wake of the blast, a statement from the inspector general said.

Balochistan has witnessed a spate of attacks in recent months.

Last month, an attack on Chinese engineers in Balochistan was thwarted by Pakistan's military, leaving two militants dead and the Chinese workers unharmed, according to police.

In March this year, at least nine police officers were killed and 11 others injured in a suspected suicide blast.

This is a developing story. More to come.