Dutch police have arrested three men and a woman and seized firearms and cash in connection with a major international organised crime investigation involving Gardaí and the PSNI.
Authorities in Amsterdam say it is one of the biggest hauls of illegal weapons there in recent years.
Earlier this week four men were arrested in connection with the same investigation in Dublin, Belfast, Offaly and Tipperary.
Dutch police raided a number of commercial properties in Amsterdam today following a tip off from Gardaí.
They seized 165 guns including new Glock pistols, 7,000 rounds of ammunition, silencers, laser-sights, computers, mobile phones and €20,000 in cash.
Three men and a woman aged between 27 and 53 were arrested - they are due to appear in court in Rotterdam on Friday.
Earlier this week, four men were arrested in Dublin Belfast, Offaly and Tipperary in connection with the same investigation.
Three of the men remain in custody while one man appeared before Blanchardstown District Court in Dublin earlier today.
42-year-old Thomas Mulqueen from Pairc Clochair, Borrisokane in Co Tipperary was charged with the possession of heroin and cannabis for sale or supply.
20 kilos of heroin and 10 kilos of cocaine, with an estimated street value of four million euro, as well as 40 firearms were seized on Tuesday in Dublin and Belfast.
He was remanded in custody to Cloverhill Prison until next week.