Five Russians have been arrested in southern France on suspicion of planning an attack, local prosecutors have said.

Four of the suspects, all from the Caucasus region, were detained in Montpellier and a fifth was arrested around 40 miles away in Beziers on Monday.

Prosecutors said certain "products" were recovered during searches of addresses linked to the suspects. Midi Libre newspaper reported that a cache of explosives was found.

The arrests came after three Islamists killed 17 people in attacks in Paris over three days.

It was not immediately clear if the latest arrests were connected to the investigation into the violence at the offices of satirical magazine Charlie Hebdo and a kosher supermarket. Reports claimed they may have been arrested in connection with organised crime.

Four men accused of having links to the jihadists who staged those attacks were due to appear in court on Tuesday.

The Paris prosecutor's office said the four men are suspected of providing logistical support to Amedy Coulibaly, who shot dead a policewoman and then killed four people after seizing hostages inside a kosher supermarket.

Meanwhile, a Bulgarian court has agreed to extradite a French national with alleged links to the two gunmen who carried out the attacks on the Charlie Hebdo offices.

Fritz-Joly Joachin, 29, told the district court in Haskovo that he was prepared to return to France to clear his name after a European arrest warrant was issued against him, charging him with participation in an organised crime group and links to a network allegedly organising the transfer of volunteers to fight with extremists in Syria.

France has been on high security alert since the attacks earlier this month.

Chechnya, a predominantly Muslim region in Russia, has seen the largest demonstrations against cartoons of the Prophet Mohammed published by the magazine.

Authorities said around one million people attended a state-organised rally in Chechnya on Monday.

The government has come under pressure in the Dáil over the status of public nursing homes earmarked for closure.