Police are investigating an arson attack on a Catholic Church in Derry last night.
The incident, at Holy Family on Aileach Road, Ballymagroarty, took place just after 10pm.
Police said an outbuilding was first set alight but that the blaze quickly spread to the church.
The parochial house was evacuated while 20 firefighters tackled the "intense" fire.
NIFRS Group Commander Andy Burns was said: "At about 10.10pm Fire & Rescue Service received a call to a shed on fire. On arrival crews encountered a well developed fire at the rear.
"The fire was very intense and spread onto the roof of the chapel. The crews battled temperatures well in excess of 150 degrees celcius."
Commander Burn said four appliances, an aerial unit and 20 crew battled the fire into the early hours, finishing at the scene around 12.50am on Saturday morning.
He said CCTV from the scene showed a group of young people entering the back of the premises just before the fire started - and that this has now been handed to police.
"There were people in the parochial house at the time having a meeting," he added.
"We had to evacuate them."
Commander Burns has urged young people in Derry not to get involved in behaviour that puts lives at risk and takes firefighters away from incidents that are not 'deliberate'.
He added: "My message to the young people in Londonderry is to not get involved in this type of behaviour - there were people in this property. We are challenging them to think if it had been their mother, father or grandfather.
"It was quite and intense fire and we had quite a bit of work to do."
PSNI Detective Constable Fielding said: "An outbuilding adjacent to Holy Family on Aileach Road was set alight at around 10.30pm. The blaze spread to the church and nearby parochial house causing damage to both. The outbuilding was completely destroyed.
"At this stage we believe two males may have been involved in starting this fire and we are keen to identify them. We would like to hear from anyone who was in the area at around the time of the fire or anyone who may have information regarding this crime.
"The number to call is 101, please quote reference 2311 24/05/19."
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