Seven wild Asian elephants, including calves, were killed when a high-speed train collided with a herd crossing the tracks in north-eastern India, local officials say.

They say another calf was injured in the incident early on Saturday in Hojai district, Assam state.

The Northeast Frontier Railway says the train driver spotted dozens of elephants and used the emergency brakes - but some animals were still hit.

Five carriages derailed after the collision, but no injuries were reported among passengers and staff on the Delhi-bound express. Train cancellations and diversions were reported in the area during the day.

The killed elephants were later examined by veterinarians and buried.

Assam has one of the biggest elephant populations in India, with nearly 6,000 animals recorded in the state.

Local railway tracks are often crossed by elephant herds - but Saturday's incident happened at a location that was not a designated elephant corridor, the Northeast Frontier Railway says.