Anti-terror police are searching dense woodland northeast of Paris after two gunmen suspected of killing 12 people in the Charlie Hebdo magazine attack were sighted.

Two men reportedly fitting the descriptions of brothers Said and Cherif Kouachi stole fuel and food from a petrol station near Villers-Cotterets, in the northern Aisne region, 43 miles (70km) from Paris, on Thursday morning.

Heavily-armed police have finished searching the village of Crepy-en-Valois, 10 miles (16km) from the petrol station.

They are now focusing on a stretch of countryside spanning from Soissons, through Abbaye de Longpont, right up to Villers-Cotteret.

Sky's Joey Jones, at the scene, said officers were going house-to-house "scrutinising each resident".

Witness Benoit Verdun told Sky News he believes the suspects are in a very large forest near Longpont, which he said is "bigger than Paris" - measuring some 13,000 hectares, or 50 square miles.

Crepy-en-Valois' mayor Bruno Fortier said he could not confirm reports the men were holed up in a house in the area.

"It's an incessant waltz of police cars and trucks," he told Reuters.

Jones said the picture is one of "utter confusion" and there are many rumours flying around.

Earlier the men, wearing balaclavas, were spotted travelling on the N2 road in the direction of Paris in a Renault Clio which had weapons on its back seat and its number plates covered.

AFP said the pair had Kalashnikovs and what appeared to be a rocket-launcher.

RAID, the French anti-terrorist unit, and GIGN, a paramilitary special operations unit, have been deployed in the region.

But Jones said it would appear the suspects are "a step or two ahead" of authorities at the moment.

Officials said the French nationals, both in their 30s and the sons of Algerian-born parents, are linked to a Yemeni terror network.

The pair are on a US no-fly list, but American officials would not give further details, including whether they fought in the Middle East with extremist groups.

Islamic State radio praised the killers as "heroes" and said they had avenged the Prophet Mohammed.

On Wednesday night, police raided an apartment in the city of Reims in the search for the killers. Seven people were arrested.

Another suspect handed himself in to police after he was named on social media as 18-year-old Hamyd Mourad.

Sky sources say the teenager, who has been arrested, is the brother-in-law of the suspects.

French Interior Minister Bernard Cazeneuve said a total of nine people are now in custody and more than 90 witnesses have been interviewed.

Tensions remain high in the country after a female police officer was shot dead in southern Paris on Thursday morning.

A "criminal" blast was also reported at a kebab shop near a mosque in the eastern French town of Villefranche-sur-Saone. No one was injured.

Officials have not said if either incident is linked to the Paris terror attack.

French investigators found a dozen Molotov cocktails and two jihadist flags in the black Citroen getaway car abandoned shortly after Wednesday's massacre.

Tributes to the victims have been left near Charlie Hebdo's offices and a minute's silence was held in the French capital.

Meanwhile, one of the first people to arrive at the bloodbath gave an emotional account of what happened.

Patrick Pelloux, a columnist who is also trained as a doctor, said: "It was horrible. Many were already gone because they were shot down execution-style.

"We managed to save the others who this morning are doing well."

Next week's issue will be published despite the murders, he said, meaning his colleagues "have not died in vain".

Staff hope to print one million copies - instead of its usual run of 60,000.

Downing Street said security has been increased at UK ports following the terror attack.