Superintendent of Police (SP) Mubarak Shah among four policemen were martyred and his driver was injured by unidentified gunmen in a firing incident at Killi Deba area of the provincial capital on Thursday.
"The head and upper parts of all the four victims were targeted", said Sultan, adding that one policeman was critically wounded. Pakistan media reported the Islamic State group had claimed the Chaman attack.
Prime Minister Nawaz Sharif strongly condemned targeting of police officials in Quetta in which SP and other police officials embraced martyrdom.
Police sources said the firing incident took place in the Kali Deeba area of the city.
A suicide bomber riding a motorbike on Monday blew himself up near a police vehicle in the town of Chaman, near the Afghan border, killing the district police chief and two others.
Violence in Baluchistan has raised concern about security for projects in the $57-billion China Pakistan Economic Corridor, a planned transport and energy link from western China to Pakistan's southern deep-water port of Gwadar. No group has yet claimed responsibility.
Mineral-rich Balochistan has been plagued for decades by a separatist insurgency and sectarian killings.