Donald Trump has claimed a terror attack that left a police officer dead in Paris will "probably help" far-right candidate Marine Le Pen in France's upcoming election.

While Mr Trump said he was not explicitly endorsing Ms Le Pen, he believes she will be helped by the attack that also saw two officers injured, because she's the candidate who is “strongest on borders, and she's the strongest on what's been going on in France.”

The comments came hours after the US President wrote on Twitter: “Another terrorist attack in Paris... The people of France will not take much more of this.

“Will have a big effect on presidential election!”

Mr Trump did not mention any specific candidates in his tweet, before mentioning Ms Le Pen in an interview with Associated Press. US presidents typically avoid weighing in on specific candidates running in overseas elections. But Mr Trump suggested his opinion was no different from an average observer, saying, “Everybody is making predictions on who is going to win. I'm no different than you.”

Analysts predict the atrocity in Paris could also bolster conservative Francois Fillon. Both he and Ms Le Pen have sought to capitalise on the terror attack, which follows a series of Isis-linked massacres that have left more than 230 people dead in France since 2015.

Ms Le Pen and Mr Fillon declared “war” on Islamism, both vowing to protect citizens with bolstered police forces and immigration crackdowns.

The Front National (FN) leader claimed a war was being waged aiming to “subject France to a totalitarian ideology”.

Gunman attack on the Champs-Elysees Show all 23 1 /23 Gunman attack on the Champs-Elysees Gunman attack on the Champs-Elysees Police officers secure the area after a gunman opened fire on Champs Elysees. One police officer has been killed, and a second injured by a gunman on The Champs Elysees Getty Images Gunman attack on the Champs-Elysees Police officers block the access of a street near the Champs Elysees in Paris after a shooting in which one police officer was killed and another wounded. The attacker was killed in the incident on the world famous boulevard that is popular with tourists Getty Images Gunman attack on the Champs-Elysees Police officers control passersby near the Champs Elysees in Paris after a shooting. One police officer was killed and another wounded today in a shooting on Paris's Champs Elysees, police said just days ahead of France's presidential election. The attacker was killed in the incident on the world famous boulevard that is popular with tourists. Getty Gunman attack on the Champs-Elysees People run away after a shooting at the Champs Elysees in Paris Getty Images Gunman attack on the Champs-Elysees French people hold their hands in the air after a shooting in which a police officer was killed along with the attacker and another police officer wounded in an attack on the Champs Elysees in Paris EPA Gunman attack on the Champs-Elysees Bystanders are frisked by police officers near the Champs Elysees avenue in Paris, France, after a fatal shooting in which a police officer was killed along with an attacker AP Gunman attack on the Champs-Elysees People hold their hands up as they walk towards police officers before being controlled near the site of a shooting at the Champs Elysees in Paris. France's interior ministry said the attacker was killed after opening fire on police in the early evening on the world-famous boulevard Getty Images Gunman attack on the Champs-Elysees Police look through binoculars as officers secure the area after a gunman opened fire on Champs Elysees Getty Images Gunman attack on the Champs-Elysees A tourist is blocked by French soldiers next to the Champs Elysee Avenue during ongoing police operations after a shooting in which two police officers were killed along with their attacker and another police officer wounded in a terror attack near the Champs Elysees in Paris, France EPA Gunman attack on the Champs-Elysees A tourist is blocked by French soldiers next to the Champs Elysee Avenue during ongoing police operations after a shooting in which two police officers were killed along with their attacker and another police officer wounded in a terror attack near the Champs Elysees in Paris, France EPA Gunman attack on the Champs-Elysees French Police officers, after a shooting in which two police officer were killed along with their attacker and another police officer wounded in an attack near the Champs Elysees in Paris, France EPA Gunman attack on the Champs-Elysees Forensic experts and police officers examine evidence from a police van on the Champs Elysees in Paris, France, after a fatal shooting in which a police officer was killed along with an attacker AP Gunman attack on the Champs-Elysees Police investigators inspect the car used by the attacker on the Champs Elysees Avenue after a policeman was killed and two others were wounded in a shooting incident in Paris, France Reuters Gunman attack on the Champs-Elysees A French soldier patrols on the Champs Elysees in Paris after a shooting. One police officer was killed and another wounded today in a shooting on Paris's Champs Elysees, police said just days ahead of France's presidential election. France's interior ministry said the attacker was killed in the incident on the world famous boulevard that is popular with tourists Getty Images Gunman attack on the Champs-Elysees Police officers patrol near the site of a shooting at the Champs Elysees in Paris Getty Images Gunman attack on the Champs-Elysees French military secure the area after a gunman opened fire on Champs Elysees Getty Images Gunman attack on the Champs-Elysees French military secure the area after a gunman opened fire on Champs Elysees Getty Images Gunman attack on the Champs-Elysees Police secure the area after a gunman opened fire on Champs Elysees in Paris, France Getty Images Gunman attack on the Champs-Elysees One police officer has been killed, and a second injured by a gunman on The Champs Elysees Getty Gunman attack on the Champs-Elysees Police officers secure the area after a gunman opened fire on Champs Elysees Getty Images Gunman attack on the Champs-Elysees Police secure the area after a gunman opened fire on Champs Elysees. Getty Images Gunman attack on the Champs-Elysees French Prime Minister Bernard Cazeneuve, flanked by Interior Minister Mathias Fekl and Justice Minister Jean-Jacques Urvoas, speaks to the media outside the Elysee Palace after a defense council meeting in Paris, France EPA Gunman attack on the Champs-Elysees A damaged window is pictured on the Champs Elysees boulevard in Paris AP

“This war is being waged without pity and without respite… the response must total across the entire country,” she added.

“I call for the awakening of our people’s ancient soul, capable of opposing a bloodthirsty barbarism.”

She called for France to reinstate border checks and to arrest all suspects on France’s “fiché S” terror watch list, while deporting foreign suspects and removing French citizenship from dual nationals.

Mr Fillon has also put security centre stage in his campaign, vowing to increase police officers by 10,000 and prison places by 16,000, while stripping French jihadis who fight abroad of their nationality and banning them from returning to France.

Like Ms Le Pen, he has proposed an overhaul of the Shengen agreement that allows border-free movement through Europe and called for a new European border police force and an annual immigration quota.

Mr Fillon echoed his rival in claiming that “Islamist totalitarianism” should be the priority of France's next president, adding: “We are at war, there is no alternative, it's us or them.”

Paris shooting: Police search home after Champs-Elysees attack

The centrist frontrunner, Emmanuel Macron, said he would also have French security in mind, pledging to increase police and gendarme numbers by 10,000 and improve intelligence services.

For several months, polls have forecast Ms Le Pen and Mr Macron to progress to the second round of the election, with the centrist former finance minister expected to easily beat the radical candidate.

But debates have seen the left-wing candidate Jean-Luc Melenchon enjoy a surge in support, amid a recovery by the former Prime Minister Mr Fillon, whose chances were damaged by a scandal involving payments to his wife.

Thursday’s attack came days after police foiled an “imminent” bombing plot believed to be linked to the election, with the first round of voting starting on Sunday.

Isis flags were found at the suspects’ homes and the group also claimed responsibility for the Champs Elysees shooting, identifying the attacker as a “fighter of the Islamic State” using the war name Abu Yusuf al-Baljiki.

The Prime Minister said the government has reviewed its already extensive election security measures and says it is “fully mobilised” for Sunday's vote, deploying 50,000 police and 7,000 soldiers.

Bernard Cazeneuve attacked Ms Le Pen and Mr Fillon for seeking to turn Thursday's atrocity "into an opportunity" for their campaigns.