The spotlight will be turned on the response of police after a man was found dead inside a unit two days after emergency services were called to the property for a welfare check.

Emergency services first visited Ocean St in Merewether, Newcastle, just after 9.30am on Sunday over a concern for welfare but were unable to raise the occupant, NSW Police said.

Newcastle City Police District officers continued their investigation before police revisited the unit on Tuesday, finding the man dead inside.

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A critical incident, which is an incident involving a NSW police officers that leads to death or serious injury, has been declared.

A Critical Incident Team from the Port Stephens-Hunter Police District will lead the investigation, NSW Police said.

It will be reviewed by the Professional Standards Command and monitored by the Law Enforcement Conduct Commission.

A report will be prepared for the Coroner.