The suspect in a deadly knife attack in central Paris on Saturday evening is a French citizen born in 1997 in Russia's republic of Chechnya, sources say.

Named by media as Khamzat Asimov, he was on a French watch list of people who could pose a threat to national security, the sources said.

Police shot dead the attacker in the busy Opéra district after he killed a man and injured four other people.

The Islamic State (IS) group said it was behind the attack.

French President Emmanuel Macron tweeted (in French): "France has once again paid in blood , but will not give an inch to the enemies of freedom."

Later on Sunday, a judicial source said that a friend of the suspect had been detained for questioning in the eastern city of Strasbourg.

France has been on high alert following a series of attacks. More than 230 people have been killed by IS-inspired jihadists in the past three years.

What do we know about the attacker?

The suspect was not carrying any identification papers and has not yet been officially named.

Sources told French media the man had no criminal record and his parents had been held for questioning. He is believed to be a French citizen who was naturalised in 2010.

He shouted "Allahu Akbar" (God is greatest) during the attack, witnesses said.

The man tried to enter several bars and restaurants but was blocked by people inside.

Police first tried to stop the assailant with a Taser before shooting him dead, nine minutes after he began the attack.

God will deliver us from terrorist.

France is one of the foolish supporters of Islam...

They should continue bombing them!