The accused reached the petrol pump at Aggar Nagar last night and attacked its manager, Bhagwan Singh, with sticks as he was on his way to deliver the day's earnings to the owner, they said.
After attacking Singh, the miscreants snatched the bag and fled from the spot, police said.
Singh has been admitted to a hospital, where he is undergoing treatment.
A case of robbery has been registered against the unidentified persons, police said, adding, efforts are on to nab the culprits.