Four persons were killed whentheir motorcycle rammed into a stranded truck on national highway six in West Bengal's Howrah district on Monday, police said.Three persons were travelling on the two-wheeler from Kolaghat to Uluberia along NH 6 when the vehicle lost control and hit the stranded truck at Bagnan area, early on Monday, they said.The three bikers killed in the accident were identified as Vicky Das, Pritam Mondal and Tanay Pachal.The helper of the truck Pankaj Sinha was also killed in the accident, police said.