The motorcycle-borne miscreants attacked Singh when he was at his office, adjoining his home, in the district's Bhikhiwind village, the police said, adding that the accused then fled the spot
Singh, 62, had fought bravely against terrorism in the state for years and was attacked by terrorists many times in the past.
Singh's security cover was withdrawn by the state government a year ago on the recommendation of Tarn Taran police, his brother Ranjit said, adding that their entire family had remained on the hit list of terrorists.
The Ministry of Defence in 1993 awarded him the Shaurya Chakra. Many documentaries have been made on his bravery.