Authorities are warning that rage could tip over into serious unrest and are concerned at the knock-on effect on tourism

Europe's debt-mired southern rim is becoming increasingly concerned by the prospect of anarchy on the streets this summer, as seething anti-austerity threatens to boil over into something more sinister.

Protests, strikes and sit-ins have long since become the norm for Greece, Italy and Spain. But some authorities are warning that rage is on the verge of tipping over into serious violence, and concerns are mounting over the knock-on effect on tourism, a vital source of income for southern Europe.

In Italy, military, police and intelligence officials are hammering out an emergency security plan for combating violent anarchy in the wake of a recent spate of violent attacks on individuals and institutions.

"The risk of escalation exists," said interior minister Annamaria Cancellieri, adding that the government was prepared to send out the armed forces to protect sensitive targets if necessary.

The Equitalia tax offices in charge of collecting unpaid debts seems to be taking the brunt of public anger. Laid-off Fiat factory workers recently occupied a tax office in Sicily, and protests outside the Naples office turned violent. Several petrol bombs were thrown against a tax office in Tuscany last week.

Last week a small but violent group of Greek and Italian anarchists claimed responsibility for kneecapping the head of Ansaldo Energia, a nuclear engineering firm owned by Finmeccanica. Roberto Adinolfi was shot in the leg as he left home for work last Monday. Authors of the letter claiming responsibility said they were the Olga cell of the Federazione Anarchiste Informale (FAI). The group said it was named after Olga Ikonomidou, one of eight anarchists jailed in Greece. They said there would be seven more attacks to avenge the jailing of the other activists.

Government officials began heightening security at approximately 400 "sensitive" locations this week, with 24-hour surveillance initiated at Finmeccanica and Equitalia tax offices, as well as for several at risk individuals. Another 1,500 soldiers were detailed to maintaining public order, bringing the total to more than 4,000. As well as corporate offices, they will protect the contested high-speed train (TAV) line under construction between Turin and Lyons, according to Corriere della Sera.

In Spain, protests have largely been peaceful, with the exception of masked radicals in Barcelona who smashed windows and lit street fires during a general strike in March. But the conservative government is taking no chances, promising to tighten up laws on public protest. Street violence, it claims, will send the country's already dangerously high bond yields soaring.

Proposals for toughening up laws include making trades unions, associations and political parties pay for any vandalism by its members during protest marches.

"I am deeply worried about the proposed changes to the law," said Cándido Méndez, head of the General Workers Union.

Sanctions for "disobeying public authorities" (meaning the police), are also set to be increased.

In Greece, bursts of anarchy and civil disobedience have sporadically infected the anti-austerity protest movement. Far from subsiding, it shows every sign of growing as Greeks prepare to head back to the polls in a climate of deepening political division and uncertainty.

"We are at the end of our tether and, of course, are planning protests and strikes against policies that have done nothing but lead to poverty and wretchedness," said Nikos Kioutsoukis, general secretary at GSEE, the country's biggest labour force.

"In the private sector, wages went down by 25.4% in 2011 alone. Overload a donkey, and as they say, its back will eventually give in."

Much, says Kioutsoukis, will depend on what government emerges next month. "If they decide to continue with measures that are taking us to the bottom of the sea," he insists, "the summer won't be hot it will be boiling."

It is a view shared in the cafes and student campuses around the capital. "The time has come to show those wankers in the IMF and EU that we are not going to take any more lying down," said Takis Tasios, a computer programmer who said he had been out of work for the past year. "I'm sick of being treated as a number by some technocrat who has no idea."

Authorities admit they are worried. Athens, once one of Europe's sleepiest capitals, now resembles a garrison town with riot police stationed on every corner. The police force is the only part of the public sector that is expanding. Greece, after all depends on tourism, and none more so than this year when unemployment has reached a record 21.7 %.

In a country with a thriving anarchist community and anti-establishment bloc, 'resistance' is a word that is never far away: it is scrawled in graffiti, large and small, over the facades of buildings nationwide.

"The system is rotten and it has to be destroyed," the KKE communist party which has also vowed to step up opposition against keeping Greece in the EU proclaimed last week. "The battle has to be unremitting."