Reports from Portugal that the metro systems in Lisbon and Oporto, Portugal's second-largest city, have shut down because of the strike, and that the ferry service linking the two sides of the Tagus river in Lisbon is also suspended.
Portugal's airport operator ANA urged passengers to check on the status of their flights before heading to the airport, but air traffic controllers were not taking part in the strike.
The country's biggest union -- the General Confederation of Portuguese Workers -- called the strike in February to complaint against a reform of the labor code that makes it easier to hire and fire workers.
Portugal, facing its most evil recession since the 1970s, was forced to take a bailout from the European Union and International Monetary Fund in May last year after running up large debts. Some economists say it might need a second bailout as the recession deepens, putting its budget targets in doubt and jeopardizing its planned return to the bond markets late next year.
The centre-right coalition government, which has a majority in parliament, and the main opposition Socialist Party gave their blessing to the bailout situation in May 2011.
Portugal was the third EU country after Greece and Ireland to receive such a bailout.