Pakistan's restive Balochistan province, according to media reports.
The explosion occurred in the Mastung district, Geo News reported.
An official said that the explosion took place near the mosque where people were gathering to mark Eid Miladun Nabi, the birth anniversary of Prophet Muhammad.
Mastung Assistant Commissioner Atta Ul Munim said that the explosion, which seems to be of a «massive» nature, took place near Madina Mosque.
At least 13 people were killed and 70 others injured in the blast, the Dawn newspaper reported.
Station House Officer (SHO) Javed Lehri said that the wounded are being shifted to a medical facility while an emergency has been imposed in the hospitals.
«Some of the injured are in critical condition,» the administration added