A senior police officer who offered himself as substitute hostage to an Islamic terrorist has died of his wounds after a supermarket siege ended in a fusillade of bullets.

In a Twitter post announcing Lieutenant-Colonel Arnaud Beltrame’s death on Saturday morning (French time), Interior Minister Gérard Collomb said the nation  would never forget “his heroism, his bravery, his sacrifice”.

Le lieutenant-colonel Arnaud Beltrame nous a quittés.
Mort pour la patrie.
Jamais la France n’oubliera son héroïsme, sa bravoure, son sacrifice.
Le coeur lourd, j’adresse le soutien du pays tout entier à sa famille, ses proches et ses compagnons de la @Gendarmerie de l’Aude. pic.twitter.com/I1h8eO7f9a

— Gérard Collomb (@gerardcollomb) March 24, 2018

Four people died – including the gunman – and another 16 were injured when Muslim fanatic Redouane Lakdim, 26, yelled “Allahu Akbar” (God is greatest) and opened fire in the Super U supermarket in the southern France town of Trèbes .

President Emmanuel Macron said Lieutenant-Colonel Beltrame, 44, “saved lives and did honour to his corps and his country” after the French leader met with Prime Minister Edouard Philippe and was briefed by security officials.

Mr Macron wrote on Twitter that he “particularly welcomed the courage of the superior officer of the Gendarmerie who, by voluntarily substituting for the hostages, has saved lives and is honouring his weapon and our country”.

Lieutenant-Colonel Beltrame volunteered to be the last hostage during the attacks in southern France and had been “fighting against death” for several hours before finally succumbing to his injuries.

“Now he is fighting against death and all our thoughts are with him and his family,” Mr Macron had said while heroic officer hovered at the brink of death.

During Friday's supermarket standoff, the assailant "let all the hostages go, except one woman he kept as a human shield. A police officer, Arnaud Beltrame — widely praised as a hero — offered to take her place." https://t.co/MDGyaofgWg pic.twitter.com/sjPm2Td6OV

— CBS News (@CBSNews) March 23, 2018

The senior officer knowingly put his life on the line after Lakdim was persuaded to swap a female hostage – a deal that allowed the woman to escape but most certainly sealed the fate of the policeman, whose uniform marked him as a living symbol of the “infidel state”.

https://twitter.com/Tom_Antonov/status/977275518071472129

Keeping his cool in his final moments, Lieutenant-Colonel Beltrame placed his active mobile phone on a table, allowing security forces to hear what was happening inside the supermarket, Mr Collomb told reporters after the incident ended on Saturday.

When the phone relayed the sound of shots, special forces intervened and “took down” the gunman in a hail of bullets.

It was then they found the 45-year-old officer, his life’s blood pouring from open wounds.

The violence began on Friday morning in the historic town of Carcassonne, where Lakdim hijacked a car, killing one passenger – whose body was later found hidden in a bush – and injuring the driver.

He then shot and wounded a policeman who was out jogging, before driving to Trèbes, where he ran into the supermarket, killing two people – a customer and store employee – before taking others as hostages.

French media reported that Lakdim had demanded the release of Salah Abdeslam, the surviving suspect in the Bataclan attacks in Paris in November 2015, which killed 130 people.

Le Parisien newspaper has identified the the gunman as being of Moroccan background who reportedly made a trip to Syria and was active on fundamentalist Sunni Islam forums.

Policemen at work as a van is taken away outside the Super U supermarket of Trebes in southern France. Photo: Getty

Trèbes, a small town of about 6000 people along the Canal du Midi in south-western France, was in lockdown on Friday (local time), with helicopters and masked police patrolling Lakdim’s neighbourhood.

In Paris, the Eiffel Tower dimmed its lights at midnight as a mark of respect for the victims and a minute’s silence was held at the Stade de France before a football match between France and Colombia.

Top anti-terror prosecutor Francois Molins said Lakdim had convictions for carrying a banned weapon and for drug use.

“He had been on a watchlist for his radicalisation and links to the Salafist movement,” Mr Molins told reporters in nearby Carcassonne, adding that Mr Lakdim had been tracked for his online contacts with extremists.

President Macron said a claim of responsibility by the Islamic State extremist group was “currently being analysed”.

“I invite all our fellow-citizens to be conscious of the gravity of the terrorist threat, but also of the strength and resistance that our people has displayed every time it has been attacked.”

Friday’s violence follows a killing spree in the nearby city of Toulouse and Montauban, where jihadist Mohamed Merah, shot seven people including school children in 2012.

Islamists associated with Islamic State have claimed more than 240 innocent French victims since 2015 , including the massacre at the satirical newspaper Charlie Hebdo, the November attacks in Paris and the truck attack of 2016 during Bastille Day festivities in Nice.

-with AAP/AFP