A man with a knife attacked six people at the Gare du Nord train station in Paris on Wednesday morning, leaving one with major injuries, a police spokesperson said.
The attacker was shot several times by police and taken to hospital with life-threatening injuries, the spokesperson added.
The man's motives were not immediately clear, police said. The Paris prosecutor said in a statement that a criminal investigation had been opened.
One police source said the officer who shot the attacker was off-duty.
The station is one of the busiest in Europe and a major link between Paris, London and the north of Europe.
Police secured the area following the attack, which happened around 0645 CET (0545 GMT).
Radio franceinfo, quoting rail operator SNCF, said trains were operating normally.