The demand at Craigavon Emergency Department is 'exceptionally high', according to the Southern Health Trust.
In an online alert the Trust has urged those with non critical or life-threatening injuries to use the Minor Injuries Unit in Dungannon.
Their statement said: "Demand on our hospital system is currently exceptionally high and will remain so for the rest of today.
"People should only come to the Emergency Dept. if seriously ill or injured and need to be immediately treated.
"For injuries that are not critical or life threatening please use the Minor Injuries Unit in South Tyrone Hospital, Dungannon which is open until 9.00 pm."