Seven people were killed while four others were injured after a trailer truck rammed into a bus from behind on the Yamuna Nagar-Panchkula highway in Haryana's Ambala, the police said on Saturday.

The mishap took place under the limits of Shahzadpur Police Station on Friday. The injured persons were rushed to a nearby hospital.

Bir Bahan, Shahzadpur Police Station SHO told ANI that a loaded trailer truck rammed into the bus moving ahead of it from behind.

"Prima facie it appears that the truck driver dozed off on the wheels and ended up ramming into the bus," he said, adding that the accident was so fierce that the trailer truck overturned on the wrong side.

The drivers of both vehicles are out of danger. Further investigation into the accident is underway, he added.

(With Inputs from ANI)