Thousands of police and soldiers have already been deployed to tighten security. Photo: Reuters

He said such resources were crucial to dealing with an expanded extremist threat, with 3,000 people currently requiring surveillance across France.

Mr Valls was laying out the government's plans following attacks in Paris in which 17 were killed.

Earlier, a prosecutor gave details on four men charged over the attacks.

Three of the men are alleged to have helped supply arms to Amedy Coulibaly, who is believed to have shot dead a policewoman on 8 January, a day before attacking a Jewish supermarket in Paris where four hostages were killed.

On 7 January, brothers Said and Cherif Kouachi attacked the Paris offices of satirical magazine Charlie Hebdo, killing 12. All three gunmen were shot dead by police.

Paris prosecutor Francois Molins said that international co-operation with authorities in Turkey, Spain and Belgium would continue, as investigators sought information on possible accomplices, the suspects' travel records, and information about how they got their weapons.

'Relentless fight'

Announcing new counter-terrorism resources, Mr Valls said security forces would be provided with better weapons and protection, including bullet-proof vests.

"We will pursue this fight against terrorism relentlessly," he said.

The new jobs will be created over a period of three years. Some 1,400 will be created through the interior ministry, mostly in counter-terrorism intelligence, with other posts to be opened at the ministries of justice, defence and finance.

Manuel Valls said that nearly 3,000 individuals need to be monitored today. Nearly half of these are people who have been or are planning to go to Syria and Iraq to join Islamic State. The others are from older radicalised networks. One lesson of the Kouachi-Coulibaly attacks is that these older networks cannot be neglected.

Intelligence experts in France say it takes 20 officers on the ground to provide round-the-clock monitoring of a suspect. Obviously this is impossible for 3,000 individuals.

Recruiting more men and women for gumshoe work will help. But the higher priority is for analysts: people who can make sense of masses of accumulated electronic information.

The French prime minister also stressed the threat resulting from people travelling to fight in Syria and Iraq.

"One thing is certain. The number of people who are radicalised and capable of carrying out attacks on our soil hasn't stopped increasing," he said.

Of those who the authorities need to monitor, Mr Valls said there were now nearly 1,300 people residing in France and suspected of links to networks active in Syria and Iraq - a number that had increased by 130% in a year.

He said there were another 400-500 people suspected of links to older extremist networks, and others who were active in the francophone "cyber-jihadist" sphere.

More Muslim clerics

Mr Valls announced a series of other measures, including:

• Sixty extra Muslim clerics to be recruited to work in prisons, in addition to the 182 already employed
• Special sections in prisons for extremist detainees
• An internet site to inform the public about ways of preventing youth radicalisation

France has deployed more than 10,000 troops across the country to protect public spaces and sensitive sites such as schools, synagogues and mosque.

Authorities in several European countries apprehended terrorist suspects following the Paris attacks. In Belgium, two men alleged to have been planning an attack against the police were shot dead in an anti-terror raid last week.

As European Commission officials met on Wednesday to discuss the extremist threat, Vice-President Frans Timmerman said Europe faced a "huge challenge" to reassure Jews about their future in Europe.