“Five persons were killed and 15 others injured in the attack,” a police official said.
A rescue operation is under way and security forces have also cordoned off the area.
Police said the injured have been shifted to nearby hospitals for treatment, while emergency has been declared at Civil Hospital Quetta.
Police have cordoned off the area and a bomb disposal squad has been requested.
There was no immediate claim of responsibility, but Taliban militants and Baloch nationalist often carry out such attacks.
The blast in Kuchlak is the fourth in Balochistan in less than a month’s time.
A week before, on July 30, five persons, including two policemen, died when a powerful bomb tore through a police patrol van at a busy roundabout in Quetta.
At least 32 people including Additional SHO Shafaat Ali were also wounded in the attack targeting the police vehicle parked outside the City Police Station at Bacha Khan Chowk.