Four people have been wounded, two of them seriously, after an axe was used during a fight on a suburban train outside Paris, a police source said.
One of the victims had their hand severed and another had their skull split open, the source added, asking not to be named. Two others were less seriously injured.
Several people, some of them minors, were involved in the fight that broke out at about 8am (0700 GMT) on Monday, the source added.
The incident happened while the RER suburban express train was at Ozoir-la-Ferrière station, south-east of Paris.
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Since the train was halted at a station, the violence did not affect traffic on the RER E line, which runs east-west through Paris and its suburbs, the state rail operator SNCF said.