Police forensic teams, paramedics and fire investigators were called to the flats on Stanhope Road, shortly after 10am on Sunday morning, after reports of concern for a man living there.
A man was found dead at the scene and a police investigation is ongoing at the flats, which were cordoned off at both the front and rear.
The identity of the dead man, believed to be in his early forties, has yet to be released.
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Simon Harris, who lives in the flats, said the news of the man's death had come as a shock.
Mr Harris, a resident at the flats for the last six years, said the dead man had lived there for a similar length of time.
"I can't come up with the words of how I feel about this," he said.
"I have known him for a long time and he was a good friend.
"He would help anyone out if he could.
"He was a happy-go-lucky lad.
"I only saw him last night, I am pure devastated."
A spokesman for Northumbria Police said: “At 10.06am we got a report from people expressing concern for a man at an address in Stanhope Road.
“Police officers went to the address, and the man has been found dead at the scene.
“Inquiries are ongoing.”
Neighbours said they had seen smoke and heard reports of fire damage.
A spokesman for Tyne and Wear Fire Service said: “We have an officer at the scene at the request of the police.”