Paris, France: A French soldier patrolling at the Louvre museum Friday shot and seriously injured a machete-wielding man who yelled "Allahu Akbar" ("God is greatest") as he attacked security forces, police said.

Prime Minister Bernard Cazeneuve said the attack, less than 80 days before presidential elections, was "terrorist in nature." 

Police held hundreds of tourists in secure areas of the renowned museum in central Paris after the assailant was shot five times around 10:00 am (0900 GMT) in a public area inside the complex.

The knifeman is in a serious condition while one soldier received a "minor" head wound and has been taken to hospital, security forces said.

Two backpacks carried by the assailant were checked by bomb disposal specialists at the scene and were found not to contain explosives.

The incident sparked fresh jitters in a country still reeling from a string of terror attacks over the last two years and under a state of emergency since November 2015. 

US President Donald Trump tweeted that a "new radical Islamic terrorist has just attacked in Louvre Museum in Paris. Tourists were locked down. France on edge again. GET SMART U.S.".

- 'Sad and shocking' -

Witnesses described scenes of panic as shoppers, sightseers and workers fled.

"We heard gunshots. We didn't know what it was about. Then we evacuated the employees and we left," a man who works in a restaurant in the Louvre told AFP, asking not to be named.

A woman colleague said: "We saw death coming for us, with everything that's happening at the moment. We were very, very scared."

The lucrative Paris tourism industry has been a major casualty of the terror attacks, with visitors cancelling or shortening their stays.

Thousands of troops have been deployed to guard the capital, with groups of soldiers with automatic rifles a regular sight inside the Louvre and around its sculpture-filled gardens.

Security forces simulated an attack there in early December to rehearse for such an emergency.

"It's so sad and shocking... we can't let them win, it's horrible," British tourist Gillian Simms, who was visiting Paris with her daughters, told AFP on Friday.

The huge former royal palace in the heart of the city is home to the Mona Lisa and other legendary artworks.

The attacker was shot in a shopping area that leads to the museum.

"The people who were in the museum -- there were about 250 of them -- were held at a distance and confined in secure areas of the Louvre," city police chief Michel Cadot told reporters outside.

A second man whose behaviour was "suspicious" has been arrested, Cadot said, without giving further details.

- String of attacks -

The string of assaults began in January 2015 when jihadist gunmen rampaged through the Charlie Hebdo satirical newspaper. Another attacker killed shoppers in a Jewish supermarket, with a total of 17 people dead in three days of bloodshed.

Ten months later, gunmen and suicide bombers from the Islamic State jihadist group attacked bars, restaurants, a concert hall and the national stadium in Paris on November 13, 2015, killing 130 people.

And last July, a Tunisian extremist rammed a lorry through crowds celebrating Bastille Day in Nice on France's south coast, crushing 86 people to death.

In between, there have been other attacks on security forces and scares, sometimes involving unstable assailants with mental health problems. 

In November, police said they had arrested members of an alleged jihadist terror ring planning attacks in Paris around Christmas.

The economy, immigration and security are the biggest issues for voters ahead of this year's presidential and parliamentary elections which had been forecast to confirm the country's tilt right after five years of Socialist rule.

But long-time rightwing presidential favourite Francois Fillon has been ensnared in a parliamentary expenses scandal over the last week, introducing new uncertainty in the unpredictable race.

Anti-immigrant far-right leader Marine Le Pen is hoping for a boost from the scandal and Trump's election, while 39-year-old centrist independent Emmanuel Macron is also climbing in the polls.

Friday's incident came on the very day that Paris was submitting its formal bid dossier to host the 2024 Summer Olympics.

The Louvre was already suffering from a fall in visitor numbers after the series of attacks in France.

Over the last two years, numbers have fallen by about two million, imperilling its claim to be the most visited museum in the world.

Last year, there was a 15-percent slump in visitors compared to 2015, to around 7.3 million.