According to Balochistan Home Minister Mir Sarfaraz Bugti, the three militants were killed when security forces launched a search operation in the Dasht area of the district.
"They acted on an intelligence tip off and when they combed the area the militants retaliated," Bugti said.
He said one of the killed militants had been identified as a key commander of the Balochistan Republican Army.
A spokesman for the Frontier Corps said the militants were part of a group that was involved in the killing of outstation labourers who were working at Shadi Kor Dam.
Also Read
Nawab Akbar Bugti was killed during a military operation in 2006 in the Dera Bugti district.
Four other militants were killed later in the evening in the Kohlu district when security forces were carrying out a search operation, Spokesman Khan Wasey said.
"All four belonged to an banned outfit and security forces have located and destroyed five of their sanctuaries in the area," Wasey said.