Gardai expect there may be further violence arising from the weekend murder in Amsterdam of Derek Dunne, one of the Republic's leading heroin traffickers and son-in-law of the leading criminal, George "the Penguin" Mitchell.
Mitchell's whereabouts were unknown yesterday but he is believed to have been in Amsterdam when Dunne, who was married to his daughter Rachel, was shot dead in an armed confrontation at his home in a quiet suburb in the west of the city.
According to Garda sources Mitchell had provided protection for his son-in-law's drug smuggling operation, and the killing is seen as a direct assault on Mitchell's organisation.
Mitchell, who left Dublin in 1996 after unsuccessfully attempting to set up an ecstasy factory in Lucan, has a considerable reputation among Irish criminals. He also has well-established connections with other organised criminal gangs in the Netherlands and Britain.
Dutch police have released very little information about Saturday's armed confrontation in Amsterdam, in which a Dutch national was shot in the head and chest. He is described as critically injured but stable in hospital. It is believed this man confronted Dunne at the front door of his house and that Dunne shot him.
It is understood the Dutch man and two associates had captured an English criminal who worked with Dunne and forced him to take them to Dunne's house.
The Englishman, whose hands were, bound was shot in the side during the confrontation but was not seriously hurt. He too was in protective custody last night.
A police spokesman said Mr Dunne and the two injured men now in custody were "unknown" to the force. He confirmed that at least six shots were fired at the scene and a revolver was recovered, although no drugs were found.
He ruled out a link between the incident and the killing of three Irishmen in a suburb of The Hague four weeks ago by a drugs gang. It was not believed that any other Irish people were involved, added the spokesman.
After the shooting at least two men drove off in a car which was later found burned out about 15km away. The Dutch police would not disclose what nationality Dutch officers believed the two or three men who escaped from the scene to be.
However, according to local media reports, it is believed the men may be of Eastern European extraction.
In recent years organised criminal gangs from former Yugoslavia and other eastern European countries have been expanding their operations in the Netherlands and are vying for control of parts of the drugs trade in which Irish criminals are involved.