Several thousand public service workers have taken part in a rally at Belfast City Hall as part of a one day strike over spending cuts and planned redundancies in the civil service in Northern Ireland.
Rallies were also held in other towns around the North.
About 60,000 staff walked out in the one-day stoppage which disrupted public transport and education.
The cross-border Enterprise rail service between Belfast and Dublin was suspended today.
The strike is due to end at midnight.
The department of health said arrangements were in place to ensure critical services were maintained.
Unions representing ambulance workers have criticised an emergency management step which forced crews taking place in a public sector strike to return to work.
The Northern Ireland Ambulance Service last night declared a "major incident" in response to the number of staff threatening to take industrial action.
It claimed that cities like Belfast and Derry would have been left without any ambulance cover.
The declaration of a major incident activated contingency protocols which compelled staff to turn up for work.
The mass strike by health, education, transport and civil service workers protesting against job cuts and the Stormont House political deal began at midnight.
Bus Éireann services between Belfast and Dublin will run as normal in both directions, although Translink coaches will not operate on cross-border routes.
Translink say the Belfast to Dublin bus service at 11.00pm tonight will operate as normal.
Most of the teaching unions are not joining the walk out, but pupil numbers may be significantly down due to lack of public transport.
Union leaders have warned that today's action will be the biggest in many years.
Workers are angry at Stormont budgets that have cut millions of pounds from public spending, a voluntary redundancy scheme to reduce the Civil Service by 20,000, and a proposed cut in corporation tax in Northern Ireland.
Members of the Unison, Unite, Nipsa and GMB unions working in health, education, the Civil Service, transport and a range of other public services will strike.
The fate of the redundancy scheme, next year's Stormont budget and the devolution of corporation tax powers from Westminster to Belfast are shrouded in uncertainty after a political row over welfare reform threatened the Stormont House Agreement in which those proposals were included.
