General strikes in Spain and Portugal will spearhead the day of action called by European unions and joined by activists as anger over governments' tight-fisted policies boils over.

For Spain, the eurozone's fourth-largest economy where one in four workers is unemployed in a deep recession, it is the second general strike in eight months in protest against draconian budget cuts.

Spain's main CCOO and UGT unions have urged people to rally under slogans such as "They are taking away our future!", deploying pickets during the night at airports, bus and railway stations.

Activists alerted social networks of an evening rally outside the parliament in Madrid.

The action comes as Spain's right-leaning government and Socialist opposition discussed how to combat a surge in home-owner evictions, blamed for two suicides in just 15 days.

Neighbouring Portugal, where protesters booed visiting German Chancellor Angela Merkel on Monday when she came to support Lisbon's austerity policies, will also hold a general strike.

Protests are being called in some 40 towns and cities across the bailed-out nation, including Lisbon and Porto.

The impact of strike may be undermined by legislation requiring a minimum service in both Spain and Portugal, but airlines have nevertheless warned of a large number of cancellations.

Iberia, Iberia Express, Air Nostrum, Vueling, Air Europa and easyJet cut more than 600 flights including some 250 international routes. Ryanair said no flights had been scrapped yet.

Portugal's TAP said it was grounding more than 160 flights, most of them international.

Greece is the epicentre of the eurozone's debt crisis but its unions are focused on the national crisis and it has limited its protest to a three-hour work stoppage and a rally in Athens.

Despite passing a hotly contested 13.5-billion-euro package of austerity measures last week, Athens is battling to convince its international rescuers to unlock the next bailout payment to stave off collapse.

Greece's finance minister, Yannis Stournaras, warned Tuesday of a "very high" risk of default.

Italian unions, too, are seeking a four-hour work stoppage.

The European Trade Union Confederation said it was the first time that it had organised a day of industrial action that included simultaneous strikes in four countries.

"By sowing austerity, we are reaping recession, rising poverty and social anxiety," the union confederation's general secretary Bernadette Segol said in an online statement.

"In some countries, people's exasperation is reaching a peak. We need urgent solutions to get the economy back on track, not stifle it with austerity. Europe's leaders are wrong not to listen to the anger of the people who are taking to the streets."

Short of taking full strike action, unions and activists in other European countries say they, too, plan to support the "Day of Action and Solidarity" against austerity and in favour of jobs.

Union-led rallies are being called across France, Belgium and in Poland, where workers decry "social and wage-dumping" in their country.

High-speed Thalys rail services between Belgium and Germany have also been cancelled for the day.

In Germany, viewed by many in southern Europe as the paymaster behind the austerity drive, the union federation DGB has called protests across the country including in Berlin and Frankfurt.

"For now it is mostly people in southern Europe suffering from a crisis they are not responsible for. But the consequences will surely be felt in the rest of Europe," it said.

AFP