A speeding passenger train Thursday killed four elephants in eastern India after the driver failed to see them in time, a state government minister said.

The express train rammed into the animals near the forests of Marghat in West Bengal state, some 620 kilometres (385 miles) north of the state capital Kolkata, forest minister Hiten Barman said.

"Four full-grown elephants were crushed to death before dawn on Thursday. The train knocked down the elephants due to negligence of the driver," Barman told AFP.

Train accidents involving elephants are frequently reported from across the country with the most recent incident in March resulting in the death of one near Buxa nature reserve, also in West Bengal state.

In December last year, five elephants were killed in a train accident in neighbouring Orissa state.

"Train accidents of this sort have of late become a concern in the northern districts of West Bengal," Barman said, adding that according to official figures at least 42 elephants had been killed in the state since 2004.

India's former rail minister Pawan Kumar Bansal stressed the need to protect the elephants from trains, describing the animals as "gentle giants" whose lives must be safeguarded, during a speech in March.

The country is home to around 25,000 Asian elephants but their numbers are dwindling mainly due to poaching and the destruction of their habitats by human populations.