Almost 15,000 extra police and troops have been mobilised to boost security across France
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Three days of terror
France and freedom
Police in southern France have detained five Chechens on suspicion of preparing an attack, prosecutors say.
The arrests took place in Beziers and Saint-Jean-de-Vedas, near Montpellier.
They come as France remains on high alert following attacks in Paris that killed 17, including 12 at the offices of satirical magazine Charlie Hebdo.
Four men charged with supporting Amedy Coulibaly, one of the gunmen behind the attacks, are due to appear in court in Paris later on Tuesday.
It is not known whether the arrest of the Chechens is connected to the attacks in Paris earlier this month.
One suspect was arrested in the city of Beziers and another four were detained near Saint-Jean-de-Vedas, according to local media.
Certain "products" were recovered during police searches, officials said, without giving further details. Unconfirmed reports said a stash of explosives was found.
Chechnya, a highly restive and predominantly Muslim region in Russia, has seen large demonstrations against cartoons of the Prophet Muhammad published by Charlie Hebdo last week.
First to face charges
Three days of attacks began in Paris on 7 January when brothers Cherif and Said Kouachi burst into the offices of Charlie Hebdo, killing 12 people.
Coulibaly killed four Jewish hostages on 9 January before being shot dead by police. He is also believed to have shot dead a policewoman the day before.
Lassana Bathily, who hid customers at the Jewish store from the gunman, is being awarded a French passport
The Paris prosecutor's office said the four men in court on Tuesday - the first to face charges in the Paris terror attacks - were suspected of providing logistical support to Coulibaly.
The men, aged 22 to 28, are expected to be placed under formal investigation.
They were among 12 people arrested in police raids on Friday. Three of the women detained in the raids were freed on Saturday and five people were released overnight on Tuesday.
Almost 15,000 extra police and troops have been mobilised to boost security across France since the Paris attacks.
Hundreds of soldiers are also being deployed across Belgium following a series of anti-terror raids and arrests.
Meanwhile, a Malian employee who helped shoppers during the supermarket siege by Coulibaly is due to receive French nationality on Tuesday.
Lassana Bathily, a 24-year-old Muslim, hid customers inside a basement cold store when the gunman stormed the shop and took people hostage.
He will receive a French passport at a ceremony in his honour after his application was fast-tracked.
It comes after a petition was circulated calling for him to be granted citizenship.
He has lived in France for nine years and applied for citizenship last year.
How the attacks unfolded (all times GMT)
Wednesday 7 January 10:30 - Two masked gunmen enter Charlie Hebdo offices, killing 11 people, including the magazine's editor. Shortly after the attack, the gunmen kill a police officer nearby.
11:00 - Police lose track of the men after they abandon their getaway car and hijack another vehicle. They are later identified as brothers Said and Cherif Kouachi.
Thursday 8 January 08:45 - A lone gunman shoots dead a policewoman and injures a man in the south of Paris. Gunman later identified as Amedy Coulibaly.
10:30 - The Kouachi brothers rob a service station near Villers-Cotterets, in the Aisne region, but disappear again.
Friday 9 January 08:30 - Police exchange gunfire with the Kouachi brothers during a car chase on the National 2 highway northeast of Paris.
10:00 - Police surround the brothers at an industrial building in at Dammartin-en-Goele, 35km (22 miles) from Paris.
12:15 - Coulibaly reappears and takes several people hostage at a kosher supermarket in eastern Paris. Heavily-armed police arrive and surround the store.
16:00 - Kouachi brothers come out of the warehouse, firing at police. They are both shot dead.
16:15 - Police storm the kosher supermarket in Paris, killing Coulibaly and rescuing 15 hostages. The bodies of four hostages are recovered.
Three days of terror