A police officer has been killed in the French capital, in an attack the president says has the hallmarks of terrorism.
"A man immediately got out and opened fire on the police vehicle, fatally wounding a police officer".
The claim of responsibility came unusually swiftly for the group, which has been losing territory in Iraq and Syria.
Paris police spokeswoman Johanna Primevert said the attacker targeted police guarding the area near the Franklin D Roosevelt metro stop on the Champs Elysees on Thursday night (local time) at the centre of the avenue, which is popular with tourists. She said he appeared to act alone.
The attacker was being investigated over his possible intention to kill police officers, sources close to the investigation said.
Paris police and soldiers have sealed off the area around the Champs-Elysees after an attack on police, ordering tourists back into their hotels and blocking people from approaching the scene.
The Islamic State group claimed the shooting, days before French presidential elections, via its Amaq news agency, naming the attacker as Abu Yousif the Belgian.
Officers at the scene said they were searching for a potential second assailant, and Brandet said it could not be ruled out that there was another or others involved.
A police union Twitter account said the officers were shot while in a vehicle stopped at a red light.
Hollande, who is not running again for office in an election said: "We shall be of the utmost vigilance, especially in relation to the election".
Hollande held an emergency meeting with the prime minister Thursday night and planned to convene the defense council Friday morning.
Speaking in Washington during a news conference with Italian Prime Minister Paolo Gentiloni, U.S. President Donald Trump said the shooting "looks like another terrorist attack" and sent condolences to France. "Some were crying. There were tens, maybe even hundreds of them".
France has lived under a state of emergency since 2015 and has suffered a spate of Islamist militant attacks that have killed more than 230 people in the past two years.
"Police operation taking place in the Champs Elysee area", they said.
Candidates in the election said they had been warned about the Marseille attackers. Security is high around the vote after France has been attacked in recent years.
A witness identified only as Ines told French television station BFM that she heard a shooting, saw a man's body on the ground and the area was quickly evacuated by police.
A French television station hosting a televised event with the 11 candidates running for president briefly interrupted its broadcast to report the shootings.
The famous wide street that leads away from the Arc de Triomphe that had earlier been crowded with Parisians and tourists enjoying a spring evening remained closed off hours after the incident. The risk for the main candidates was that misjudging the public mood, making an ill-perceived gesture or comment, could damage their chances.