Striking Italian union workers have marched through more than 50 towns and cities to protest against government economic reforms they say erode their rights.

Thousands of protesters clashed with police in some cities, including Milan, where students dressed as Santa Claus jumped the fence at a regional government office building. Police dispersed that protest with tear gas.

The general strike, which shut down basic services across Italy, is the first by two of the country's largest union groups against a centre-left government which has traditionally courted the unions.

It created a patchwork of chaos as trains, buses, schools, ports and other services closed down.

Prime minister Matteo Renzi said the right to strike must be protected but insisted his tougher line is necessary to return the economy to growth and create jobs.

"The future belongs not to those who are afraid but those who have the courage and the desire to change," Mr Renzi said.

In a sign of discord within his own party, some members of the Democratic Party joined the marches. Stefano Fassina, a former deputy economics minister, told Sky TG24 it was important that someone from the party marched alongside the workers.

CGIL leader Susanna Camusso led a protest march in the northern city of Turin, headquarters of car maker Fiat and a symbolic city for Italy's shrinking industrial might. She said changes need to be made "with and not against the people".

The unions are protesting over spending cuts and labour market reforms that will make it easier for firms to fire workers.