At least three persons including a policeman were shot dead by unknown attackers in different parts of the city here on Monday, police said. According to details, some unknown armed attackers opened fire on a policeman, Malik Fayyaz, in Kemari area and killed him on the spot. One more unidentified person was shot dead in Korangi area while another person who sustained bullet wounds in firing at Lyari Khadda Market, succumbed to injuries in Civil Hospital. Police registered cases of the incidents and started investigation.