An off-duty police constable died after he was attacked on his way home from a night out, police said.
A murder investigation has been launched after 28-year-old Pc Gareth Francis was assaulted in Edgeley, Stockport. Two men have been arrested on suspicion of his murder.
Police were called to a report of an assault on Castle Street, Edgeley, at around 1.20am on Sunday.
Emergency services attended the scene within minutes and discovered Pc Francis with a serious head injury.
The officer was walking home from a night out with friends when he was attacked, Greater Manchester Police (GMP) said. They had been dropped off by taxi in Edgeley after he and his friends enjoyed a night out in Manchester city centre.
The motive for the attack is still being investigated but police confirmed they were not treating it as a robbery and that they do not believe a weapon was used.
His colleagues paid tribute to a "dedicated officer" who had been serving with GMP for six years. It is understood Pc Francis, from Stockport, was not married and did not have children but that he did have a girlfriend.
Stockport divisional commander Chief Superintendent Chris Sykes said: "First and foremost I would like to pass on my condolences to both Gareth's family and his colleagues in South Manchester.
"Gareth was a dedicated police officer with six years' experience and he will be greatly missed by his colleagues. However, the loss will be even greater for Gareth's family and I would like to reassure them that we have a team of detectives working round-the-clock now to establish exactly what happened this morning."
Ian Hanson, chairman of Greater Manchester Police Federation, said: "Gareth was a much-loved and well respected member of the GMP family. We are all distraught at this news. Understandably, his team are devastated. Our immediate thoughts at this time are with his family, friends, colleagues and his partner."