The two brothers believed to be responsible for Wednesday’s terror attacks in Paris remain at large as the search of a vast forest where they were thought to have sought sanctuary enters its third day.

Overnight, Parisians again took to the streets of their city to watch the lights go out on the Eiffel Tower in an unprecedented display of outrage and unity.

As the suspected mass killers Chérif and Said Kouachi continued to evade a huge manhunt, the millions who reacted with horror, then fear, then defiance, to the attack on the satirical magazine Charlie Hebdo refused to be cowed by another day of violence.

As the lights went out on Paris’s most famous landmark, hundreds of armed police were combing woodland and fields outside a small town to the capital’s north-east. Military helicopters circled overhead in an operation to pinpoint the suspects who had eluded police for more than a day.

The Eiffel Tower lights went out last night in tribute to the victims of the Charlie Hebdo massacre (EPA)

After nearly 24 hours without a confirmed sighting of the brothers following the assault in central Paris which left 12 dead, the biggest counter-terrorism operation in recent French history moved its focus to the 5,000-strong community of Crépy-en-Valois after the brothers broke cover and held up a petrol station on one of the main routes from the capital.

Staff at the Avia service stop in Villers Cotterets in the Aisne region reported seeing rocket propelled grenades and assault rifles in the back of the Kouachis’ stolen grey Renault Clio as they were forced to fill its tank at gunpoint at about 10.30am (9.30am GMT).

One resident said it appeared that police believed the men may have fled into the nearby Foret de Retz - a vast woodland measuring 13,000 hectares. A homeowner, who like hundreds of other residents had been ordered by police to stay inside and lock all doors, said: “The police arrived at 5pm and ordered us to stay indoors, lock up and close the shutters. I’m a bundle of nerves.”

The pair are thought to be in Crépy-en-Valois (Graphic by John Bradley)

The potential endgame to the Charlie Hebdo shooting came after France suffered a second day of terrorist bloodshed as it entered three days of national mourning for the atrocity which left eight journalists dead at the satirical weekly, including its editor, and two police officers.

A female police officer suffered fatal injuries when a gunman, wearing a bulletproof vest and armed with a pistol and an automatic weapon, opened fire on her and a colleague in Montrouge, a southern suburb of Paris, shortly before 9am (8am GMT) before fleeing on foot. The dead officer was named as Clarissa Jean-Philippe.

The French authorities said the shooting was being treated as a “terrorist act” but no formal link had been identified with the Charlie Hebdo killings. The second officer was seriously injured. Two people were tonight being held in connection with the incident.

The suspected copycat attack occurred as France came to a standstill to observe a minute’s silence at midday and the bells of Notre Dame Cathedral in Paris tolled in memory of the victims of the Charlie Hebdo killing.

The lights on the Eiffel Tower were dimmed and flags were flown at half-mast across the country as politicians praised the spirit of defiance which saw 100,000 people take to the streets of French cities on Wednesday night to reject the actions of the attackers with the message “Je Suis Charlie”.

But as the spirit of unity flourished, so too did the first signs of a backlash against France’s Muslim population, the largest in Europe, after at least five serious attacks aimed at mosques and businesses. Dummy grenades were thrown at a mosque overnight in Le Mans, western France, and a Muslim family were shot at in the car in the Vaucluse region of southern France.

The Prime Minister Manuel Valls said that the “real France” was in the dignity and defiance of the demonstrations not in these scattered acts of anti-Muslim violence.

Cherif and Said Kouachi, reportedly 32 and 34 (PA)

“This is a time when the nation should be saying 'no' to sweeping statements, 'no' to intolerance, 'no' to hatred and 'no' to the kind of comments which traumatise the country,” Mr Valls told RTL radio.

“France is more than (the novelist) Michel Houellebecq,” he said - a reference book published on the day of the Charlie Henbdo shootings in which Houellebecq speculates about a Muslim-run France in 2022.

The lawyer for Charlie Hebdo, known for its lampooning of radical Islam and the subject of previous attacks by extremists including a firebombing in 2011, said that its next edition would go ahead on 14 January. Rather than its usual print run of 40,000 copies it will produce one million. The former Mayor of Paris, Betrand Delanie, urged people to buy a copy as a gesture of defiance. Other French newspapers promised to help the decimated Charlie Hebdo staff produce the magazine.

An unidentified man is detained in Reims

After a night in which the trail of the Cherif, 32, and 34-year-old Said appeared to have gone cold despite a number of raids in the eastern city of Reims where one of the men lived, the manhunt recommenced in a dramatic manner after the brothers pulled off the RN2 road from Paris to Soissons to steal food and petrol from the Avia filling station.

The manager reported seeing a formidable arsenal in the rear of the Clio, which was hijacked from its driver in north east Paris after the men abandoned their initial getaway vehicle - a Citroen C3 used to flee from the offices of Charlie Hebdo.

Reports that the Clio was then seen heading back in the direction of Paris led to a flurry of activity in the capital as police vehicles were stationed at the northern entrances to Paris to monitor traffic entering the city.

Police sources have cast further light on the level of preparation and the motivation of the brothers after revealing that they had left 10 Molotov cocktails in the black C3 along with a black jihadist flag and headscarf, a magnetic rooftop emergency services light and an identity card. Reports that the flag was the banner of Islamic State were later denied.

US and French intelligence believe that Said Kouachi trained in Yemen in 2011, believed to be under the auspices of Yemen-based al-Qaeda in the Arabian Peninsula, an al-Qaeda offshoot known as AQAP, officials said.

The existence of a claimed third suspect in the Charlie Hebdo killings remains unclear after the 18-year-old brother-in-law of Cherif Kouachi surrendered himself voluntarily to police, claiming he had been in school at the time of the attack.

Hamyd Mourad handed himself in on Wednesday night after seeing his name circulating on social media. He remains in custody, although initial reports suggested his alibi that he had been attending lessons had been confirmed. The French Interior Ministry said a total of nine people have been detained in relation to the killings.

The brothers Cherif and Said Kouachi are said to be “armed and dangerous”.

Chérif, 32, was already known to security officials for a previous terror conviction.

He was jailed in 2008 for three years for seeking to join extremists in Iraq as part of a jihadist group which appeared to offer instruction in how to fire the Kalashnikov rifle – the weapon used in the Charlie Hebdo attack.

Warning: Viewers may find this video distressing

The two brothers suspected of the attack are believed to be orphans of Algerian descent, raised in the city of Rennes in north west France.

In pictures: Reaction to Charlie Hebdo attack Show all 39 1 /39 In pictures: Reaction to Charlie Hebdo attack In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Pencils, representing the freedom of expression, placed in tribute in Nantes Reuters In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack France's Jason Lamy Chappuis soars through the air over a message that reads "Je suis Charlie" Getty In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Solidarity in Nice AP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Turkish citizens organised a vigil in front of the French consulate in Istanbul AFP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Graffiti decorates a London wall in solidarity with the victims of the attack in Paris AFP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A tribute of flowers and candles outside the French Embassy in Prague, Czech Republic AP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Messages of sympathy near the Charlie Hebdo office in Paris AFP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Workers install a poster reading 'Je suis Charlie' (I am Charlie) on the Palais des Festivals facade in Cannes In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A woman looks at floral tributes left outside the Charlie Hebdo magazine offices in Paris In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A woman places flowers near the offices of French satirical newspaper Charlie Hebdo in Paris In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Journalists of international press agency Agence France-Presse (AFP) hold signs reading "Je suis Charlie" (I am Charlie) at their headquarters in Paris as they observe a minute of silence for the victims of an attack by armed gunmen on the offices of French satirical newspaper Charlie Hebdo in Paris which left at least 12 dead and many others injured In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Pens and pencils are placed in the form of a peace sign over the names of late French cartoonists Cabu, Tignous, Wolinski and late Charlie Hebdo editor Charb on the Place de la Republique (Republic Square) in Paris In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Australia mourns victims of the Paris massacre at Federation Square in Melbourne In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Indian artist Sudarsan Pattnaik is pictured with his sand sculpture, in tribute of those who lost their lives in the attack by gunmen on French satirical weekly Charlie Hebdo in Paris that killed 12 people, at Golden Sea Beach in Puri, some 65 kilometers from Bhubaneswar In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A man holds a placard that reads "I am Charlie" as members of the European Parliament and citizens gather during a minute of silence for victims of the shooting at the Paris offices of weekly newspaper Charlie Hebdo, in front of the EU Parliament in Brussels In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A painting of the 'Marianne', the national symbol of the French Republic is placed between candles to commemorate the victims killed in an attack at the Paris offices of the weekly newspaper Charlie Hebdo, in front of the French Embassy in Berlin In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Pencils and flowers of condolance are placed at the French embassy at Pariser Platz in Berlin In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Mourners hold signs depicting victim's eyes during a rally in support of Charlie Hebdo, a French satirical weekly newspaper that fell victim to an terrorist attack, at Union Square in New York In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People hold up placards reading 'I am Charlie' during a gathering in Nice Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A man lights candles set near the portrait of three of the four cartoonists killed, in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A man holds the French national flag tied a black ribbon as he and others gather in Lyon to pay their respects Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Parisians gather to pay respect for the victims of a terror attack against 'Charlie Hebdo' Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People gather in front of the 'Club de la presse' in Montpellier, to show their solidarity for the victims of the attack by unknown gunmen on the offices of the satirical weekly, 'Charlie Hebdo' Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A drawing depicting cartoonist Jean Cabut, left, Charlie Hebdo editor Stephane Charbonnier, center, and cartoonist Georges Wolinski, is placed outside the French Embassy in Berlin, Germany. The message reads 'Victims of their success, R.I.P.' AP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A woman lays a candle during a gathering at the Place de la Republique in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People take part in a vigil in Trafalgar Square, London, following the deadly terror attack on French satirical magazine Charlie Hebdo in Paris PA In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People light candles forming the name Charlie during a gathering in Strasbourg, eastern France Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People stand stand in Marseille, southern France, next to a portrait of French cartoonist Georges Wolinksi, killed during an attack by unknown gunmen on the offices of the satirical weekly, 'Charlie Hebdo' Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People hold placards reading in French 'I am Charlie' during a gathering at the Place de la Republique in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A man holds a placard reading 'With all our heart with Charlie Hebdo, Freedom of the press: Our freedom' during a gathering in Marseille, southern France Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack The French and European union flags fly at half-mast at the French Embassy in Washington, DC Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People gather at the Place Royale in Nantes to show their solidarity for the victims of the attack in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Flowers, candles and a sign reading 'I am Charlie' are placed against a wall during a demonstration in Paris AP In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Journalism students hold a banner reading in French: 'Journalism students : Solidarity' as they raise pens during a gathering at the Place de la Republique in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People gather for a rally in solidarity with the killed Charlie Hebdo employees, in Geneva, Switzerland EPA In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack A man holds a placard reading: 'Freedom of the press is priceless, fundamentalism, of any kind, will not pass' as others hold up placards reading in French, 'I am Charlie' during a gathering at the Place de la Republique in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack Journalists raise their press cards as others hold up pens during a gathering at the Place de la Republique, following the terrorist attack on the offices of the satirical weekly, 'Charlie Hebdo' Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People hold candles at a rally in support of the victims of Wednesday's terrorist attack, at the Place de la Republique in Paris Getty Images In pictures: Reaction to Charlie Hebdo attack Reaction to Charlie Hebdo attack People gather in front of the city hall of Rennes, western France, following the attack in Paris Getty Images

Prime Minister Valls told RTL radio early this morning the two men were known to intelligence services and the fear that they could carry out another attack "is our main concern."

The murder of nine journalists, two police officers and a maintenance man by masked men has shocked France. At around 11.30am two men forcibly entered the offices of the satirical magazine, where a weekly editorial meeting was taking place, and after compelling the journalists to identify themselves opened fire. They were last seen fleeing the building.