Paris terror attacks: France's Prime Minister seeks tighter surveillance as police say weapons used in massacres were from abroad

France’s Prime Minister will seek to tighten the surveillance of convicted criminals, following police reports suggesting that the weapons used to carry out the deadly terror attacks in Paris last week came from outside the country.

Manuel Valls warned in a speech on Tuseday that "serious and very high risks remain" in France, and called for new measures to monitor imprisoned radicals.

Christophe Crepin, a French police union representative, said several people were being sought in relation to the "substantial" financing of the three gunmen – the Kouachi brothers and Ahmedy Coulibaly.

Said and Cherif Kouachi sparked a three-day man hunt after they attacked the offices of the satirical magazine Charlie Hebdo, where they singled out its editor and his police bodyguard for the first shots before killing 12 people in all.

In turn, the brothers' friend, Amedy Coulibaly, killed four hostages in a kosher supermarket, before he was shot dead by police on Friday.

Mr Crepin added that the combination of the weapons being sent from abroad, the amount sent and the logistics of the attacks indicated the trio were members of an organised cell.

While the militants behind the attacks claimed to hold allegiances with al Qaida and Isis – groups which view each other as enemies - Mr Crepin said he believes the attackers held little loyalty to individual jihadi groups.

French authorities are now working to trace the source of the weapons funding, and scouring Paris for a Mini Cooper registered to Hayat Boumeddiene, Coulibaly's widow, who Turkish officials say is now in Syria.

Meanwhile, a Bulgarian a prosecutor has revealed that a man being held there in custody had ties to one of the brothers who carried out the attack on the magazine Charlie Hebdo.

The developments come after French police warned yesterday that as many as six members of the terrorist cell that carried out the Paris attacks could still be at large, including a man seen driving a car registered to Boumeddiene.

Responding to last week’s brutal attacks, officials have deployed 10,000 troops in France to protect sensitive sites, including Jewish schools and synagogues, mosques and travel hubs.

In a move symptomatic of the tensions in the country, a man who had praised the terror attacks in a drunken rant to police was swiftly sentenced yesterday to four years in prison.

In the UK, Prime Minister David Cameron and Home Secretary Theresa May have also used the Paris attacks to argue for increased powers of surveillance by reviving the abandoned draft communications data bill, previously labelled a “snoopers’ charter”.

Additional reporting by PA