The occupants of the flat were uninjured but two Police officers who entered the building were taken to hospital for smoke inhalation.
Cllr Neil Kelly said: “Lives could have been lost in this arson attack. This could have been a terrible tragedy had somebody been killed, especially at Christmas time.
“I must praise the brave actions of the two Police officers who entered the building despite the clear danger which confronted them. They put their own lives at risk to protect the public. I hope they will be able to make a swift recovery.
“The people behind this arson attack have no regard for the lives of others; they must be apprehended by the Police. If anybody has any information about this attack then I would urge them to contact the PSNI or Crimestoppers.”