Two journalists were injured in a knife attack near the former officers of satirical newspaper Charlie Hebdo in Paris.
Police initially announced four people were wounded in the attack but they now say only two have been confirmed as wounded.
A suspect was arrested after they were detained near the Bastille plaza in eastern Paris, said Paris police.
The official said police are still searching the area while they question the arrested suspect.
French Prime Minister Jean Castex said the victims were journalists and that they were taking a cigarette break when the attack occurred.
He added that a second suspect has been arrested.
An investigation was opened into “attempted murder in relation with a terrorist enterprise”, according to an official at the prosecutor’s office.
Details have not been released of the identities of the attacker or the wounded, who are in “absolutely urgent” condition, an official said.
A Paris police official said that while authorities initially thought two attackers were involved, they now believe it was only one person.
Police cordoned off the area after a suspect package was noticed nearby.
AP reporters at the scene of Friday’s police operation saw officers flooding into the neighbourhood, near the Richard Lenoir subway station.
Prime Minister Jean Castex cut short a visit to a suburb north of Paris to head to the Interior Ministry to follow developments.
The motive for the attack is unclear, and it is not clear whether it is linked to Charlie Hebdo, which moved its activities out of the area after Islamic extremists attacked its editorial offices in 2015, killing 12 people.
The trial in the Charlie Hebdo attacks is currently underway across town. Murmurs broke at the terrorism trial of 14 people, including 3 fugitives, accused of helping the attackers in the January 2015 killings, as the news filtered through.
The widows of the Charlie Hebdo attackers are scheduled to testify Friday afternoon.
Earlier this month French President Emmanuel Macron defended the satirical newspaper as he criticised what he called “Islamic separatism” in France.
