A police officer and a shooter were killed on Paris's iconic Avenue des Champs Elysees at 9.30 PM on Thursday. The Islamic State group claimed responsibility for the attack, which hit just three days before a tense presidential election, as candidates appeared on national TV on a program called "15 Minutes Pour Convaincre (15 Minutes to Convince)" , a final collective appearance.

Helicopters and sirens could be heard across central Paris - and ambulances, police cars and bikes could be seen in the neighbourhood of the most famous avenues in the city.

One officer was killed and two police officers were seriously wounded when the attacker stepped out of a car and opened fire with an automatic weapon on a police van, media reports say. The assailant was killed in retaliatory police fire.

President Francois Hollande has said it is a terrorist attack and will hold a security meeting on Friday morning.

The Champs Elysees has been cordoned off as have three central Paris metro stations - George V, Champs-Elysees Clemenceau and Franklin Roosevelt. Armed police officers, some with shields and riot gear are keeping the public away. The officers declined to comment on the unfolding situation.

Earlier this week two men were arrested on charges of plotting to carry out an attack in order to impact the election process.

The Islamic State group’s claim of responsibility just a few hours after the attack came unusually swiftly for the extremist group, which has been losing territory in Iraq and Syria.

In a statement from its Amaq news agency, the group gave a pseudonym for the shooter, Abu Yusuf al-Beljiki, indicating he was Belgian or had lived in Belgium. Belgian authorities said they had no information about the suspect. IS described the shootings as an attack “in the heart of Paris.”

The attacker had been flagged as an extremist, according to two police officials, speaking on condition of anonymity because they weren’t authorized to publicly discuss the investigation.

(With inputs from AP)