Officers were quickly on the scene in Glasgow's East End after reports of an incident in a tenement flat at 6.35am.
Emergency services were called to the property in Shettleston Road, close to its junction with South Vesalius Street. It is understood the man was stabbed during an incident in a first-floor flat. Police are treating the death as suspicious.
Residents claimed a woman fled from the flat through the window, which was seen lying open this morning.
Locals said they saw police officers run down the street towards the property from the nearby Shettleson Police station.
Forensic teams spent several hours combing both the flat and street for evidence. The road was cordoned off from shortly before 7am and a fleet of police vehicles were at the scene.
It is understood a Polish couple live in the flat where the incident happened.
The area is home to a large Polish community and a popular Polish cafe, Bar u Jessici, lies just doors along from where the disturbance happened.
One woman, who works at the cafe, said: "I have no idea what has happened. I haven't heard anything." Another local cafe owner, who did not want to be named, said: "I was here from 6am and it was all quiet.
"A short time later my husband said he saw police cars with flashing lights in the street and officers were beginning to cordon off the street."
Another woman said she saw a man being stretchered out of the close. He was then taken by ambulance to Glasgow Royal Infirmary where he died a short time later.
Shopkeepers with businesses within the police cordon were told they couldn't trade today while investigations were under way. Shabbir Alam, who works at Allsorts hardware store, said: "We won't be able to open up today. The police haven't told us anything about what happened."
A spokeswoman for Strathclyde Police said investigations were continuing. She said: "Police were called to reports of a disturbance in a flat around 6.35am today in Shettleston Road. A man was seriously injured and died a short time later at Glasgow Royal Infirmary. The death is being treated as suspicious."