Ambulance crews from the Republic were drafted into Northern Ireland for the second night in a row last night.
The issue arose after the Northern Ireland Ambulance Service (NIAS) found itself stretched beyond capacity.
Yesterday, a crew from here was based at Altnagelvin Hospital in Derry.
Police and members of a Protestant loyal order came under attack by petrol bombers in a night of unrest in the city.
Two petrol bombs were thrown at the Apprentice Boys Memorial Hall in the city centre from the direction of the republican Bogside area as people who had taken part in a parade earlier in the day socialised inside.
No-one was injured but police who attended the scene were then also subjected to attack, with a further 15 to 20 petrol bombs and other missiles thrown at them from nearby Fahan Street.
Looking in to Emergency Ambulance Control ... the team starting night shift getting to grips with tonights challenges ... tough place, resilient capable team ... pic.twitter.com/HfmibP1xe8— John Wright (@JW_3736) August 10, 2019
On Friday, another crew had to be based at Newry Ambulance Station.
Both services have an understanding they will help each other out in special circumstances.
A spokesperson for the Northern Ireland Ambulance Service says they were ten crews short on Saturday and they also had to use eight private and voluntary ambulances to deal with non-life threatening cases.
Speaking to the BBC yesterday, NIAS chief executive Michael Bloomfield said that on Friday night they were down 14 crews out of 52.
"That's over a quarter and our crews and our control room worked very hard to make sure that we prioritised the most critically urgent patients," said Mr Bloomfield.
"On top of that, we have had support from voluntary and private sector providers."