British intelligence officers helped foil a 'Day of the Jackal' style plot by two Islamic State fanatics to murder a French presidential candidate, it emerged tonight. (tues)

Clement Baur, 23, and Mahiedine Merabet, 29, were in a high security prison after their rented flat in Marseille was raided on Tuesday afternoon as they prepared for 'an imminent attack'.

Both French nationals were known to police as radical Islamists who had converted in prison while serving time for drugs offences.

Clement B, 23, (left) and Mahiedine M, 29 (right), have been arrested in Marseille as police say they were planning on carrying out an 'immediate' terror attack

French anti-terror police have arrested two men aged 23 and 29 who are believed to have been plotting an attack to be carried out in the next few days

Officers have found guns and chemicals used to make explosives commonly found in suicide vests inside a rented apartment, local media reports

Agents from the DGSI, France domestic secret service, found weapons in the Marseille apartment, along with TATP, the so-called 'Mother of Satan' explosives that are frequently used by jihadis.

Baur is from Ermont, north of Paris, while Merabet is from Croix, near Roubaix, and close to the Belgian border.

The pair were arrested as part of an investigation opened in Paris for 'criminal association and breach of arms legislation in connection with a terrorist enterprise'.

Each was well known to the security services and had been tailed for a number of months. The operation to bring them to justice was stepped up last week.

Police also discovered a video of the two men pledging allegiance to ISIS and a newspaper page showing the presidential candidate they planned to target, it is reported

'Intelligence about the men came from British officers working to combat terrorism in Europe,' said a source close to the case.

Police found a video made by the two men in which they declared allegiance to ISIS and a Le Monde newspaper front page showing the right-wing conservative politician FrancoisFillon.

It was part of a photomontage that included a machine gun, an Isis flag, ammunition and the words 'The Law of Talion,' after a fictional character in an intensely violent videogame.

Interior Minister Matthias Fekl said their planned assassination was due to be carried out in the 'next few days' but did not discuss potential targets.

Marine Le Pen, thefar-Right Front National candidate, was due to hold a campaign rally in Marseille on Wednesday.

Police did not discuss the details of the plot or the target, though Marine Le Pen is due to hold an election rally in the city on Wednesday

Both of the men were known to security services and thought to have been radicalised in prison. Neither of them are from Marseille, police said

Ms Le Pen confirmed photos of the men were passed to her security team on Thursday last week.

Mr Fillon, the Republicans party candidate, was also handed the images on Friday and his security was increased as a result.

An aide to Mr Fillon confirmed that the initial tip off about the plot came from British intelligence services.

Police had been hunting the suspects since the end of last week and seized them a few minutes apart in the port city, said an intelligence source.

The successful raid evoked scenes in the Frederick Forsyth novel 'The Day of the Jackal', about a plot to murder former French president and wartime leader Charles de Gaulle.

Officers have been hunting the pair since last week and arrested them within minutes of each other on Tuesday. Police are searching a rented apartment

It was later turned into hit movie starring Edward Fox as the assassin and Michel Lonsdale as the police chief who foils him.

'Everything will be done to ensure security' for the election, Mr Fekl said.

Some 50,000 police, gendarmes and soldiers will be deployed around France for each round of the presidential elections, due to take place on April 23rd and May 7th.

France is currently under a State of Emergency following a number of atrocities carried out by groups and individuals linked to ISIS and al-Qaeda.

The entrance of the Paris headquarters of Marine Le Pen, the far-right National Front candidate, was hit by petrol bombs last week.

The Molotov Cocktail attack was allegedly claimed by an anti-fascist group, although their involvement has not been confirmed.

Ms Le Pen, has long accused the government of failing to tackle militant Islamists and her adviser, Florian Philippot, said on French TV that 'our democracy itself, our voting operation and electoral campaigns are under threat'.

Far-left candidate Jean-Luc Melenchon, himself riding high in the opinion polls, sent text messages of support to Mr Fillon and Mr Macron offering his 'complete solidarity'.