Three migrants have died in southwest France after being hit by a train while they were lying on the tracks, a police spokeswoman said on Tuesday.

She said four migrants had been on the train tracks near Saint-Jean-de-Luz at around 5 am CET when they were hit by a train travelling to Bordeaux. Three died instantly, while another is seriously hurt, she said, adding that it was not clear why they were lying on the tracks.

Two of the migrants had Algerian nationality, the others' nationalities are not known.

Mayor Eneko Aldana-Douat of nearby Ciboure said on BFM TV that the area near the Spanish border is a passageway for immigrants.

The train was on a line that links the seaside resort town of Hendaye, on France's border with Spain, and the city of Bordeaux, the national railway company SNCF said.

The victims were thought to be migrants “who were sleeping or were lying ... on the railway line,'' said Eneko Aldana-Douat, mayor of Ciboure, near the crash site.

He said it's not unusual to see migrants in that region near the border.