The French government fears a wave of extreme left-wing terrorism this year with the possible sabotage of key infrastructure, kidnappings of major business figures or even bomb attacks.

Secret French government reports, seen by the Observer, describe an "elevated threat" from an "international European network ... with a strong presence in France" after the radicalisation of "a new generation of activists" in recent years. Senior analysts and experts linked to the government have drawn parallels with the Action Directe group, which carried out 50 or more attacks in the early 1980s. Others cite the example of the Baader-Meinhof gang.

A report by the French domestic intelligence service talks of "a rebirth of the violent extreme left" across Europe that is likely to be aggravated by the effects of the economic crisis. Other secret documents expose alleged links with activists in Italy, Greece, Germany and the UK. "It has been growing for three or four years now and the violence is getting closer and closer to real terrorism," said Eric Dénécé, director of the French centre of intelligence research and a former Defence Ministry consultant.

While some believe such claims to be scaremongering, the present political atmosphere is tense, with many among right-wing President Nicolas Sarkozy's aides fearing a repeat of the violence in Athens last month, when angry and alienated young people and a hard core of violent left-wing extremists rioted for several days, causing significant damage and bringing the city to a halt.

Last week hundreds of fly-posters around Paris called on young people "forced to work for a world that poisons us" to follow the example of their Greek counterparts. "The insurrection goes on. If it takes hold everywhere, no one can stop it," the posters said.

The recent intelligence reports have blamed violent demonstrations against changes in employment law in 2006, often by middle-class young people, for the recruitment of large numbers of new activists.

A series of incidents last year confirmed the fears of French police. In January two activists were arrested in possession of what was alleged to be bomb-making materials. In November nine people were arrested after a lengthy surveillance operation in the central French village of Tarnac, where they had set up a commune. Two of the alleged ringleaders, Julien Coupat, 34, and his partner Yildune Lévy, 25, are still in prison accused of sabotaging high-speed TGV railway lines and "associating with wrongdoers with terrorist aims".

Gilles Gray, assistant director of economic protection of the French domestic intelligence service, spoke recently of "a philosophy that was spreading in Europe". The arrests in Tarnac were "a strong message ... addressed to those who might be thinking about committing similar acts," he said. "We hope that this affair has put a stop for a time to this kind of violent action [and will avoid] a return of Action Directe."

Investigators believe that the arrests at Tarnac provoked "reprisals" in Athens, where the offices of the French news agency Agence France-Presse were attacked with makeshift incendiary devices, and in Hamburg, where the French consulate was daubed with paint.

A claim of responsibility for the sabotage of the TGV lines was, police say, sent to a German newspaper from Hanover and signed "those who have had enough ... in memory of Sébastien", believed to be a reference to Sébastien Briat, a young anti-nuclear militant crushed by a nuclear waste train in eastern France exactly four years before the night of the recent spate of sabotage. Coupat and Lévy had taken part in demonstrations and actions in Germany, the US and the UK.

Coupat has also been accused by investigators of anonymously writing a book, The Coming Insurrection, published by a little known Paris publishing house in 2007. The book, which has been translated into English and posted on US and UK anarchist websites, was found in the possession of three young activists arrested after detonating a bomb in a field. It contains instructions about sabotaging railways and other means of "destroying the power of the police, seizing local political power by the people, and blocking the economy". A statement from the publishing house said the author was "a committee from the subversive tendency".

But some accuse France's right-wing government of both exaggerating and exploiting the left-wing threat. "They are turning my son into a scapegoat for a generation who have started to think for themselves about capitalism and its wrongs and to demonstrate against the government," said Gérard Coupat, father of the alleged ringleader of the Tarnac group.

"The government is keeping my son in prison because a man of the left with the courage to demonstrate is the last thing they want now, with the economic situation getting worse and worse. Nothing like this has happened in France since the war. It is very serious."

Author and researcher Christophe Bourseiller told the Observer the threat was being exaggerated. "Yes, there is a certain renewed level of agitation, but there is a huge difference between deliberately slowing down a few trains without injuring anyone and something like the Madrid bomb blasts," he said. "The Ministry of the Interior has made it look like the Tarnac arrests halted a serious campaign of violence with a huge, huge media operation."

Certainly there is a widespread fear at the ministry in the Place Beauveau of violent protests in the coming months. A powerful and growing movement among schoolchildren forced the tactical withdrawal of wide-ranging reform plans after demonstrations in Lyon led to clashes with the police, mass arrests and the burning of cars.

Trade unions have promised a series of mass stoppages in the coming months. Among a population already made bitter by static salaries, rising prices and structurally high levels of unemployment, the lay-offs and wage cuts that could result from the economic crisis will fuel anger.

"Whether or not the Tarnac group is guilty, there are other groups in France, in Italy, in Germany, which, having lost faith in a political left in disarray, are tempted by violent action and are in a phase of semi-clandestinity," Alain Bauer, a criminologist at the Sorbonne, told the Observer. "With Action Directe and the Red Brigades, there was a first intellectual phase, followed by a radicalisation and then a transition to physical action. Books like The Coming Insurrection are strongly reminiscent of the first phase."

Other similarities include the tactics envisaged and the middle-class, educated profile of most of the activists.