Northern Ireland Ambulance Service reports response delays
The NI Ambulance Service says it has experienced a "sustained period of increased demand" resulting in "a delay in the response to many of our calls".
It says it will prioritise the most serious calls "to get a response to the sickest patients as soon as possible".
Calls for "less serious emergencies are still currently subject to significant delays".
It adds that the public should only phone 999 for an ambulance in the event of a serious medical emergency.
"For less serious problems you should continue to contact your own GP or local out-of-hours service in the first instance," the NI Ambulance Service said.
"Please consider alternative transport to an Emergency Department or Minor Injury Unit for lesser injuries and complaints.
"We would take this opportunity to remind the public that arrival at an Emergency Department by ambulance does not mean you will be seen or treated more quickly than self-presentation."
Patients were being advised that the most ill were being seen first.
The trust said on Tuesday evening that the number of calls received have been significantly higher than last year.