A hit team intercepted by gardai yesterday were on their way to murder the Kinahan cartel's top target Patsy Hutch, a brother of Gerry 'The Monk' Hutch, detectives believe.
Gardai suspect that they planned to lure him out of his fortified home and away from his 24/7 Garda protection using a distraction.
Three men armed with a sub-machine gun, an automatic pistol and a revolver were arrested in a van in the car park of an apartment block on Gardiner Street, Dublin, at 8am yesterday.
A fourth man in his 40s was arrested later and searches were carried out in the north inner city and north and west Dublin.
Two additional firearms were later found, including a machine gun, as well as a silencer and a quantity of ammunition.
Patsy Hutch has no involvement in crime. He has been repeatedly warned by detectives that his life is in danger.
His son, Gary, was murdered by the Kinahan cartel in Spain in September 2015. The gun attack at the Regency Hotel six months later is believed to have been in revenge for that shooting.