Four teens were wounded, two of them seriously, by an axe wielded during a fight on Monday on a suburban train outside Paris, police sources said, with the main suspect later arrested.
One of the victims -- all aged 16 or 17 -- had a hand cut off and another had their skull split open.
Two others were more lightly injured in the struggle that one police source said had broken out around 8:00 am (0700 GMT) as the teenagers involved were on their way to secondary school.
It was not immediately clear what triggered the fight, in which weapons including the axe, a knife, a samurai sword and baseball bats were used.
All the wounded people were brought to hospital and none were in danger for their life, the source added.
The main suspect, a 16-year-old, was later arrested at his home and held in custody, another police source said.
An axe was found and confiscated during the search, they added.
The incident happened while the RER suburban express train was at the station of Ozoir-la-Ferriere southeast of Paris.
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, state rail operator SNCF said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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