The man, named by French media as Farid Ikken, was shot by another policeman and is being treated in hospital.

The officer was attacked with a hammer and suffered minor injuries.

Hundreds of people were locked inside the cathedral for a time during the incident.

The BBC's Hugh Schofield, in Paris, says the profile of Farid Ikken is intriguing investigators, because it bears little relation to that of other recent lone attackers in France.

The Algerian journalist had spent some time working in Sweden and arrived in France in 2014.

He had been working for a doctorate in communications in eastern France, but lived in the Paris suburb of Cergy.

His former supervisor at the University of Lorraine in Metz told French media he was astounded to learn that Farid Ikken was involved, as he had been a strong defender of Western values. "I fell off my chair," he told French TV.

The attacker shouted "this is for Syria" as he carried out the attack.

Police have found a video pledging allegiance to so-called Islamic State (IS) at his flat.

Investigators are waiting to question Mr Ikken.

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 slit 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