Strikes by public sector workers, including teachers and health staff, over pension changes have caused widespread disruption across England.More than 70% of England's 21,700 state schools have been closed or partially closed by the action.
The Trades Union Congress said the action followed a "triple assault" on public sector pensions.
The government said the cost of public service pensions had risen by a third in a decade, so changes were needed.
Prime Minister David Cameron called the strike a "damp squib".
Marching through towns He told the Commons pension changes were "absolutely essential", and the government offer on pensions was fair.
Hundreds of thousands of teachers, civil servants, immigration staff and some NHS workers have walked out in protest at planned cuts to their pensions.
The TUC said it expected more than one million workers would take part in the strike in England.
Schools, hospitals, courts, JobCentre Plus and passport offices, airports and ports were among services disrupted, as hundreds of demonstrations were held across the country.
Public service workers and their supporters have been marching through towns and cities, including Manchester, Exeter and Nottingham.
Greater Manchester Police said about 20,000 people took part in a rally in Manchester city centre, while up to 6,000 people attended a rally in Sheffield city centre and 6,000 people were at a rally in Brighton, police said.