Assistant sub-inspector Virendra, who was in a PCR van with another policeman, stopped two people last night at Ghoda Chowk in northeast Delhi's Jafrabad.
The two tried to flee on seeing the policemen.
Virendra got out of the vehicle and caught hold of one of them. In a bid to escape, the man attacked him with a screw driver, said Deputy Commissioner of Police (Northeast) A K Singla.
The assistant sub-inspector, however, did not free the accused who was subsequently arrested, he added.
The policeman has been admitted to a hospital.