Tens of thousands of people from all over the country have converged on Spain's capital to hold a large anti-austerity demonstration.
By mid-morning several major roads had been blocked as buses unloaded protesters at 10 rendezvous points from which marches began.
The main organiser, Social Summit, an association of more than 150 organisations, and the Workers' Commissions and General Workers trade unions, said the demonstration was called to protest against government cuts during the country's financial crisis.
The Interior Ministry's regional office said it expects more than half a million people to reach Christopher Columbus Square in the centre of Madrid, where union leaders would make speeches.
Some marchers unfurled banners with slogans such as "Let's go! They are ruining the country and we have to stop them."
"This government's policies are causing too much hurt," said Ignacio Fernandez Toxo, the secretary general of the Workers' Commissions. "It's a lie that there isn't another way to restore the economy."
Large anti-austerity protests also were planned in neighbouring Portugal.
The Madrid protest comes four days after another anti-government gathering in the north-eastern city of Barcelona which police said included some 1.5 million demonstrators.
"We've had our pay cut. We don't get the firefighting training and equipment we need. There are more students and fewer teachers in our children's classrooms, and healthcare is also being cut," said fireman Carlos Melgaves who was marching in a group of about 50 firefighters. "We can't take it anymore."
Speaking in Nicosia, Cyprus, where Europe's finance ministers were meeting, Spain's economy minister, Luis de Guindos, said his government is aware it is asking sacrifices of Spanish society. "These sacrifices are absolutely unavoidable if we are to correct the difficult economic climate we are experiencing," he said. "We are laying the foundations for a recovery."