Mir had earlier survived two attempts on his life, indicating the growing peril for religious leaders in Pakistan.
His murder comes only days after two JUI-F leaders were shot dead in Khuzdar, reiterating the persistent risk for those affiliated with the political party.
The JUI (F) is the largest faction that split from the original JUI in 1980. This division was due to a disagreement over the policy of Pakistani president Zia-ul-Haq, who supported Mujahideen outfits during the Afghanistan war.