Northern Ireland health trusts cancel non-emergency operations
Belfast Health Trust has cancelled all non-urgent elective surgery up to and including Sunday 11 January due to pressures on emergency departments.
The rest of Northern Ireland's five trusts have cancelled some non-urgent elective surgeries.
It is one of a series of escalation measures put in place in order to tackle demands on the emergency system.
The Southern Trust said it had cancelled less than 10 operations and was doing so on Tuesday only.
The Belfast trust said: "This decision has not been taken lightly and will be kept under review throughout the remainder of the week.
"We would like to stress that cancer surgery and emergency cases are unaffected.
"Minor healthcare issues can be dealt with at home, by a pharmacist or by a GP."
Meanwhile, the South Eastern Trust said all of its hospital emergency departments were under "significant pressure" on Tuesday evening.
It said the Ulster Hospital, Dundonald, was facing "particular challenges".
It is not unheard of for hospitals to cancel non urgent operations in times of pressure.
But it is unusual for all five health trusts to do it at the same time.
It is an indication of just how much pressure Northern Ireland's health service is under, especially within emergency care.
The BBC has been told that the measure is being reviewed daily and was introduced after all health trusts reported an extraordinarily busy weekend.
The ED attendances for the period from 22 December last year to 15 January are 23408 with 145 waiting longer than the 12 hour target.
Last year, more than 23,000 people sought help at their emergency department when 145 people exceeded waiting 12 hours.
A national target is in place where people should not have to wait more than four hours to be seen by a doctor in the emergency system.
While a spokesperson for the Health and Social Care Board said it was unacceptable that anyone should have to wait, they stressed that Northern Ireland's waiting time figures were improving.
In 2011/12 there were 10,211 12-hour breaches, while last year that figure was slashed to 3,130.
Antrim Area hospital is reported to be the busiest on Tuesday night.
On a normal day, it sees around 200 people in its emergency department, but it is expected that figure will be exceeded on Tuesday night.
In a statement, the South Eastern Health Trust said it was experiencing "significant pressure" at all of its emergency departments and increasing emergency admissions to all its hospitals.
"We are facing particular challenges at the Ulster Hospital emergency department, and would like to remind people to only attend if they are a genuine emergency."
The trust warned patients that they may have to wait longer than usual because of the "surge in attendances".
"Our staff have gone to extraordinary lengths to ensure patients receive the highest quality of care under difficult circumstances, and we would like to pay tribute to them for their hard work," the trust said.
On Tuesday night, Health Minister Jim Wells paid tribute to health workers: "I am so grateful for the dedication and hard work of all the staff who are under huge pressure in our hospitals."
The Health and Social Care Board said: "As part of trusts' normal escalation arrangements, all trusts have had to cancel some non-urgent elective procedures to provide additional capacity to respond to the emergency pressures.
"This decision is not taken lightly and it is recognised that it causes inconvenience and frustration for patients.
"Patients requiring urgent treatment will continue to receive this. The number of cancellations will vary across trusts and trusts are reviewing the position daily to minimise the impact on patients."