At least four policemen were shot dead by unidentified assailants in Quetta's Killi Deba area on Thursday, police said.

The gunmen opened indiscriminate fire at the police mobile while it was patrolling the area, Deputy Inspector General of Police Abdul Razzak Cheema said.

Superintendent of Police Quaidabad Mubarak Shah was among the four martyred police personnel in what police said was an act of targeted killing.

Police and Frontier Corps personnel reached the site and started an investigation into the incident.

No group has claimed responsibility for the attack as yet.

Prime Minister Nawaz Sharif "strongly condemned" the attack on policemen, a tweet by PML-N said. Balochistan Chief Minister Nawab Sanaullah Zehri and Home Minister Sarfaraz Bugti also condemned the incident and directed police to apprehend the culprits involved in the assault.

The incident comes days after District Police Officer of Qilla Abdullah, his security guard and driver were killed and over 10 other people, including five police personnel, were injured in a suicide blast in the border town of Chaman on Monday.

The banned Tehreek-i-Taliban Pakistan (TTP) had claimed responsibility for the attack.