A man has died and two others, including a British man, have been injured in a knife and hammer attack on a street in central Paris.
The attack occurred near the Eiffel Tower shortly before 21:00 local time (20:00 GMT) on Saturday.
A 26-year-old French national known to security services has been arrested and anti-terrorism prosecutors have opened an investigation.
Officials confirmed that the man killed was a German national.
France’s Interior Minister Gérald Darmanin said the victim was with his wife when he was attacked and fatally stabbed on Quai de Grenelle.
He said the wife’s life was saved by the intervention of a taxi driver and that the suspect fled across a nearby bridge spanning the River Seine.
The man then attacked two more people, hitting one in the eye with a hammer, the minister said.
The suspect, named in French media as Armand R, was then Tasered by police and arrested on suspicion of assassination – defined in French law as pre-meditated murder – and attempted assassination in relation to a terrorist enterprise.
The two people injured – a Frenchman aged around 60 and a British tourist – were treated by emergency services, with neither found to be in a life-threatening condition.
The UK Foreign Office said: “We are supporting a British man who was injured in Paris and are in contact with the local authorities.”
A police operation was initiated around the Bir-Hakeim metro station on Saturday night, and authorities urged people to avoid the area.
Mr Darmanin said the alleged attacker was heard shouting “Allahu Akbar”, Arabic for “God is greatest”, and told police he was upset because “so many Muslims are dying in Afghanistan and in Palestine”.
He said the suspect served four years in jail after being convicted for planning another attack in 2016 and was on the French security services watchlist.
The man was also known to have suffered psychiatric disorders, Mr Darmanin said.
On Saturday, a video was posted on social media in which the suspect criticised the French government and discussed what he described as the murder of innocent Muslims, AFP news agency reports.
Writing on X, formerly Twitter, French President Emmanuel Macron sent his thoughts to all those affected by the “terrorist attack” and thanked the emergency services for their response.
“The national anti-terrorist prosecutor’s office will now be responsible for shedding light on this affair so that justice can be done in the name of the French people.,” he said.
It comes less than two months after a teacher was killed in a knife attack at a high school in the northern city of Arras, prompting the French government to put the country on its highest level of national security alert.