A man found collapsed by police dealing with a fight has died in hospital.
Police said the victim, aged in his 20s, was found near Park Lane Hotel, Piccadilly, central London, in the early hours of New Year's Day.
Meanwhile two men were arrested on suspicion of assault and a third man, who was taken to hospital, has since discharged himself.
Police are investigating links between the incidents but have no evidence to suggest any so far.
A spokesman said: "At approximately 0330 GMT traffic officers on routine patrol came upon a fight involving three men in Piccadilly."
He said two men were arrested and taken into custody while a third was taken to hospital.
While the officers were dealing with this incident they were alerted to a man who had collapsed in Park Lane.
The spokesman said: "The man was taken to a central London hospital where he was pronounced dead."
A London Ambulance Service spokeswoman said they were called to the area to reports a 25-year-old man was unwell.
"He was in cardiac arrest and was taken to hospital by ambulance as a priority," she said.
The spokeswoman said they received a second call to the Piccadilly area and a 26-year-old man was taken to hospital with head injuries.
Guests at the Park Lane Hotel were forced to use the rear entrance as the front remained closed.
A spokeswoman for the hotel said she did not know if the incident involved any guests.
Piccadilly has been closed eastbound between Hyde Park Corner and Down Street.