QUETTA-A policeman was shot dead in the provincial capital by unidentified persons on Thursday,police said. The police said unidentified persons gunned down a police head constable, Soba Khan, at Killi Deba and escaped from the site after committing crime. He received critical wounds and succumbed to his injuries before reaching hospital. The police has registered a case against unidentified attackers and started searching for the culprits. However, so far no group has accepted responsibility for the murder. Several policemen, mainly those from the traffic police, have lost their lives and many have been injured in target killings during past several months.