The break-in happened between 5pm on Saturday, June 4, and 9.15am on Monday, June 6, in West Park. The offender broke in found keys to a gun cabinet and stole guns that were inside.
Officers are keen to identify a man seen in the area shortly before the burglary. He is described as white, aged 40-50-years-old, of skinny build, 5ft 6ins to 5ft 7ins tall, with short greying black hair with a bald spot in the middle. He was wearing a blue/grey t-shirt.
Detective Inspector Paul Stewart said: "It is important that we find the person responsible for this burglary so that we can establish where the firearms are and ensure they are recovered before they get into the wrong hands and members of the public can help us with this.
Met Office announces yellow weather warning for thunderstorms across North East following heatwave
National Mackem Day 2022: 14 things you'll only understand if you're from Sunderland
Durham police appeal for help to find 33-year-old in connection with alleged burglaries
Sunderland drunk staggered into traffic after being found slumped at side of road
Campaigners rally against Local Plan after farmland in Cleadon earmarked for 156 homes
"It may be someone is trying to sell these on and I would ask any gun traders to be on their guard and let us know if anyone tries to sell them any of these guns - if they are caught in their possession they too could face police action.
"There were a number of people walking their dogs in the park and farmland that the house overlooks and it is possible they saw the burglar, I'd ask anyone who was in the area to come forward and speak to us. If anyone saw a man fitting this description we would also like to hear from them."
The guns stolen are: -
.22 cz2452 bolt action rifle serial number 71a477 with a sound moderator fitted
Hatsun semi automatic shotgun serial number 393314
Lamber double barrelled up and under 12 bore shotgun serial number 278006
Webley vulcan air rifle with scope and silencer.
Anyone with information should contact Northumbria Police on 101 quoting reference 208 060616 or Crimestoppers anonymously on 0800 555 111.