A Frontier Corps' spokesperson said that the security convoy was traveling from Wadh area to Bela when it struck a remote controlled explosive device planted on the roadside near Jhao area in Khuzdar district of Balochistan, killing three personnel and wounding four others.
He added that following the blast, militants who had taken positions in nearby mountains opened fire on the security personnel.
The security forces resorted to retaliatory gunfire and the exchange of fire continued till the filing of this report.
The condition of two blast victims was reported as critical.
Khuzdar is considered to be one of the most sensitive districts of Balochistan where militants have been targeting security forces and national installations for more than a decade.
Worsening law and order situation has forced hundreds of families to migrate from Khuzdar to different parts of Balochistan and Sindh.