The protest in the centre of Brussels had a festive atmosphere

Few buses and trams were running in most cities, and Charleroi airport, south of Brussels, was shut down.

Trains were not affected as unions wanted them to keep running to carry people to protests in the capital.

Tens of thousands of protesters have been marching through Brussels to get the prime minister to reconsider.

A primary school in Brussels decided to allow retired teachers and grandparents to take the lessons as part of the nationwide protest.

Unions are calling for more provision for older workers, saying that employees over 50 are often jettisoned when companies attempt to cut costs.

No talks

They also complain that in other cases, the new plans would keep older people working longer while young people struggle to find jobs.

Retired staff and grandparents took classes in one school

"If the government does not respond favourably... the atmosphere will become fiercer," Socialist union leader Xavier Verboven told local VRT television.

"November is risking to become a very turbulent month... This is a signal to the government."

Prime Minister Guy Verhofstadt's government has rejected calls to re-open talks with unions on the proposed changes to state pensions.

It is the second major strike in Belgium this month.