There were unconfirmed reports on Wednesday night that a man had died following what police described simply as a “serious incident”.
It happened in the Kirkistown Walk area of the Belvoir estate in south Belfast, off the Milltown Road.
Police sealed off the scene and a witness described crowds gathering there late in the evening.
At around 9pm, the PSNI had said that two men were seriously hurt, and that a man had been arrested.
They did not offer any further details.
Late last night, Belfast health trust said one man was in a critical condition in hospital.
It is understood that he is in his late 50s, and that he was going to undergo an operation.
It is believed another man had died.