Police have shot a man who attacked an officer with a hammer outside the Notre-Dame cathedral in Paris.
The man shouted "this is for Syria" during the attack, the interior minister said. Prosecutors have opened a terrorism investigation.
The officer suffered minor injuries. The suspect was wounded in the chest when another policeman opened fire.
Tourists fled for cover as the attack unfolded. Hundreds of people were in the cathedral at the time.
France is in a state of emergency since attacks by jihadists in Paris killed 130 people in 2015.
It is part of the US-led international coalition against IS and has conducted air strikes against militants in Syria.
The assailant on Tuesday afternoon carried kitchen knives and the identity card of an Algerian student, French Interior Minister Gérard Collomb said.
The man, who was being treated in hospital, has not been named.
France, a favourite target - Hugh Schofield, BBC News, Paris
The terrorist spotlight has swung to Britain, but no-one in France is under the illusion that the country is safe. Squads of soldiers with automatic weapons at the ready are a regular sight on the streets of Paris. France remains a favourite target for the propagandists of so-called Islamic State.
What intrigues is the similar character of four recent attacks in Paris: at the Louvre in February, where a man attacked a soldier with a machete; at Orly airport in March, where an attacker was killed after trying to take a gun from a soldier; on the Champs-Elysées last month, where a gunman killed a policeman before himself being killed; and now this.
Different from the recent UK atrocities - and the earlier French attacks in Paris and Nice - none of these recent French attacks was against random targets. They were all conducted by lone men. And they were all against clearly identified symbols of the state.
As police declared the situation "under control", hundreds of people were being allowed to leave the cathedral.
Kellyn Gorman, an American tourist, said: "I was about to come inside [the cathedral] and heard the noise, the gunshots, turned around and saw the assailant on the ground where they had shot him."
"It was very safe, very quickly contained."
Notre-Dame is one of the most visited tourist sites in Paris. Last year, police foiled an attack near the site.
The incident comes just three days after militants used a van and knives in an attack in London which left seven dead.
Recent terror attacks in France
- 20 Apr 2017 - A convicted criminal who was investigated for threatening to kill police opens fire at police on the Champs Elysees in Paris, killing one and wounding two. He is shot dead - and the assault is claimed by IS
- 3 Feb 2017 - A machete-wielding Egyptian man shouting "Allahu akbar" attacks French soldiers at Paris's Louvre Museum - he is shot and wounded
- 26 Jul 2016 - Two attackers slits the throat of a priest at his church in Saint-Etienne-du-Rouvray, in Normandy. They are shot dead by police
- 14 Jul 2016 - A huge lorry mows down a crowd of people on the Nice beachfront during Bastille Day celebrations, killing 86. IS claims the attack - by a Tunisian-born driver, later shot dead by police
- 13 Jun 2016 -A knife-wielding jihadist kills a police officer and his partner at their home in Magnanville, west of Paris. He declares allegiance to IS, and police later kill him
- 13 Nov 2015 - IS jihadists armed with bombs and assault rifles attack Paris, targeting the national stadium, cafes and Bataclan concert hall. The co-ordinated assault leaves 130 people dead, and more than 350 wounded
- 7-9 Jan 2015 - Two Islamist gunmen storm the Paris offices of satirical magazine Charlie Hebdo, killing 17 people. Another Islamist militant kills a policewoman the next day and takes hostages at a Jewish supermarket in Paris. Four hostages are killed before police shoot the gunman dead. The other two gunmen are cornered and killed by police in a siege