The Islamic State group has claimed responsibility for the shooting on Paris' Champs Elysees that killed a police officer and left two others gravely wounded, according to the Associated Press.
In a statement from its Amaq news agency, the group gave a pseudonym for the shooter indicating he was Belgian.
The attacker opened fire on a police van on the avenue before being killed.
The claim of responsibility came unusually swiftly for the group, which has been losing territory in Iraq and Syria.
And the pseudonym, Abu Yusuf al-Beljiki, indicated that the attacker already had ties of some sort to Islamic State extremists.
BREAKING: The Islamic State group has claimed responsibility for the attack that killed a Paris police officer.— The Associated Press (@AP) April 20, 2017
The shooter pulled up beside a parked police car and opened fire, he said. The driver then abandoned the car and was fatally shot while trying to flee on foot.
"Police officers were deliberately targeted," French Interior Ministry spokesman Pierre Henry-Brandet said.
In Washington, President Donald Trump said it "looks like another terrorist attack."
"What can you say?" Trump said. "It just never ends."
Meanwhile, as France's elite anti-terrorism took control of the crime scene and searched the shooter's car for possible explosives dozens of police officers kept the curious away.
"The area is dangerous because of shooting," a police officer yelled at reporters in English. "You have to stay back."
BFMTV was the first to report the shooting on one of the Paris' most famous boulevards.
The deadly shooting happened as France is in the midst of a hard-fought presidential election.
Marine Le Pen, one of the candidates and leader of France's far-right National Front, fired of a tweet in support of the officers.
"Emotion and solidarity for our security forces, again being targeted," she wrote.
Le Pen's rival, Francois Fillon, also tweeted his support. "Tribute to the security forces who give their lives to protect ours," he wrote.
Candidate Emmanuel Macron also chimed-in. "Tonight I would like to express my solidarity with respect to all of our security forces," he tweeted.
While it remained unclear what was behind the latest spasm of deadly violence in Paris, the city has had to contend with a series of terrorist attacks that have terrified the French.
The Associated Press contributed to this story.