The attack happened in Browne's Steakhouse on Main Street in Blanchardstown in the northwest of the city around 8pm.

It is understood police are investigating whether the dead man was a gunman in the initial attack and was tackled in the aftermath.

The shooting was "gang-related", RTE reported, and happened "as customers including families with children were eating out on Christmas Eve".

The two injured men were taken to Connolly Hospital for treatment.

One of the men, aged in his 20s, was pronounced dead in hospital. It has not been confirmed whether he was shot.

A post-mortem will be carried out on Tuesday.

The second man, in his 40s, was treated for gunshot wounds and was in a serious condition on Sunday night.

The scene has been preserved for a technical examination and police have requested assistance from the Office of the State Pathologist.

No arrests have been made, police said.