Video report by ITV News Correspondent Lucy Watson
Around 9,000 nurses are taking part in the UK’s first 12-hour strike action on Wednesday over pay.
The unprecedented walkout in Northern Ireland saw staff leaving patient bedsides supported by other healthcare workers, including paramedics and social workers.
Those striking belong to the Royal College of Nursing (RCN), which has not taken industrial action in its 103-year history.
Routine medical appointments have been cancelled, minor injury units closed and there will be delays to some ambulance responses and emergency departments remain open.
At the Ulster Hospital in East Belfast there was plenty of support for the striking nurses with passing motorists honking their horns in solidarity.
Ambulances leaving the major hospital sounded their sirens briefly in support.
Nurses in Northern Ireland are paid less than their counterparts in England and Wales, but for the nursing professionals that found themselves reluctantly on the picket line on Monday, the strike was as much about patient care it was about wages.
Those outside Ulster Hospital told ITV News they were "angry" and "sad" that the situation had got to this stage. One nurse of 39 years said she'd had not been able to sleep the night over her decision to strike.
"It doesn't sit well with us that we're not going in to see those patients today," Iona Mccormack told ITV News.
"I've certainly had a very sleepless night, I actually feel quite anxious and nervous. I would much prefer to be in work. But I feel for the future of our health service we must do this."
Nationalist SDLP leader Colum Eastwood said: "Every politician in Northern Ireland should be embarrassed that our nurses have been forced to strike today. I know I am.
"Let's stop the political games and sort it out."
A newly-qualified registered nurse in Northern Ireland earns £1,875 less than in Scotland and £1,419 less than in England and Wales.
For a specialist nurse, the difference is up to £4,677, the RCN said.
The union added that around half of nurses in Northern Ireland are considering leaving the profession because of pressure caused by under-staffing; at present just under 2,800 posts are unfilled.
For many of the nurses ITV News spoke to on Wednesday, striking was the "last thing they wanted to do" but they feel they have been left with no option.
Janette Cochrane, a tissue viability nurse, told ITV News the health service was currently being held together by "goodwill".
"If nurses did just do the shifts that they're supposed to do, and if weclocked on and clocked off at our exact starting times and our ending times,then the place would just fall apart," she said.
Marie McAteer, a senior officer with the Royal college of Nursing told ITV News she was "absolutely devastated" that the situation had led to strike action.
"I feel that this could have been all resolved long before now and there's not a person on this picket line that wants to be here. But we're doing it for the patients," Ms McAteer said.
"This is not all about pay for the Royal College of Nursing. This is about keeping our patients safe, having proper staffing levels, allowing our patients to have the service that they deserve and for our nurses to be able to do their own job instead of their own job and everybody else's, which they're doing at the moment."
Health authorities in Northern Ireland have been unable to break the deadlock since no ministers are in place to take decisions at the devolved parliament at Stormont.
The Executive's Department of Health had offered an extra £51 million.
Its senior civil servant, Richard Pengelly, said it was as far as he could go in the absence of ministers to take decisions on re-financing the NHS as well as ordering much-needed reforms.
There has been an impasse for more than 1,000 days due to a stand-off between Sinn Féin and the DUP on issues such as Irish language legislation and a ban on same-sex marriage.
Civil servants running public services cannot find enough extra cash to satisfy the RCN.
Spending on temporary agency staff to fill gaps has doubled.
Unison, Unite and Nipsa trade unions which cover ambulance paramedics and jobs like cleaning, portering, catering and administration are also taking industrial action.
Services like cancer care will be exempted.
All patients and service users affected by cancellations of appointments and service closures have been notified by their local health trust and appointments will be rescheduled.
The Northern Ireland Ambulance Service will be prioritising 999 calls and those calls which are less serious in nature, potentially, face a delay in response times.
Dame Donna Kinnair, chief executive and general secretary of the RCN, said: “This is a moment that every nurse wishes had never come, but faced with an abject failure to tackle unsafe staffing levels and severe pay inequality with colleagues from across the UK, our members in Northern Ireland are saying enough is enough."
Nearly 300,000 people in Northern Ireland were on a waiting list for a first appointment with a consultant, according to Department of Health figures published last summer.
A spokesperson for Health and Social Care (HSC) organisations said: “Regrettably, as a result of the widespread nature of the strike, numerous appointments and treatments have been cancelled and many services across our hospitals and the community care sector have had to be stood down or reduced.
“We sincerely apologise in advance for the distress this action will cause to everyone impacted especially our patients, service users and family members.”
The South Tyrone Hospital Minor Injury Unit (MIU), Mid Ulster MIU, Bangor MIU and Ards MIU will all be closed.
All emergency departments will remain open as normal.