By Daniel Sandford
BBC News, Rome
Large parts of Italy's transport system have been brought to a halt by a nationwide strike.
Demonstrators joined huge marches in cities across Italy
The protest led by the country's three largest unions also closed banks, post offices and government buildings.
The action by the unions, which have about 12 million members between them, was against the government's proposed spending cuts in the 2006 budget.
Demonstrations took place after the morning rush hour in squares across Italy, including Rome's Piazza Navona.
The general strike - the sixth in four years - is the strongest protest yet against what the unions say are damaging cuts in public services. They also say the budget will not help Italy's stagnant economy.
The unions want to put pressure on Prime Minister Silvio Berlusconi's centre-right government, which faces a general election next year.
In most places, public transport stopped for four hours after 0900 (0800GMT). This meant bus, tram and train services almost ground to a halt, though some skeleton services still ran.
Air traffic chaos
Italians took it all in their stride. Some did not go to work, others made sure they travelled before the strike started.
Milan commuters were hit by strike action timed for rush hour
But tourists were caught out. Many were stranded on the deserted platforms of Rome's main Termini Station in unusually low temperatures.
American Daniel Turner said "we just flew into today - we've been standing here in the freezing cold for about two hours".
An air traffic control stoppage caused the greatest chaos, with Alitalia forced to cancel more than 200 flights. But by the evening it had got its schedule largely back on track.
As well as the transport disruption, government offices were closed and hospitals said they were only operating emergency services. Banks and post offices were also shut.
In some cities the transport disruption was delayed to the end of the day.
Milan's transport strike came in the middle of the evening rush hour.
Italy did not grind completely to a halt, but the unions - the left-wing CGIL, Catholic CISL and moderate UIL - made sure their concerns were heard.
Mr Berlusconi, who faces elections next year, shrugged off the action
Protesting musicians played simultaneous renditions of Verdi's Requiem in cities across the country.
"I think that this strike will be a demonstration of how fed up Italian people are with the government of Silvio Berlusconi," one woman said at the rally in Rome's Piazza Navona.
The head of the CGIL, Guglielmo Epifani, claimed millions of people had stayed away from work.
"It shows that workers, pensioners and the young share our condemnation of both the budget and the government," he said.
But visiting Messina in Sicily, Mr Berlusconi was dismissive, saying "it's absolutely useless, a tired old ritual that will have no impact whatsoever".