The Irish Republic is to expel an Israeli diplomat over the use of fake passports in the killing of a Hamas official in Dubai.
Foreign Minister Micheal Martin said an investigation had proved that eight Irish passports used in the operation were forgeries.
Hamas official Mahmoud al-Mabhouh was found dead in a Dubai hotel in January.
Dubai police have said they are 99% sure Israeli agents were involved, though Israel says there is no proof.
Mr Martin said in a statement that Israel had been "requested to withdraw a designated member of staff of its embassy" and that he expected the request would "be quickly acceded to".
"The misuse of Irish passports by a state with which Ireland enjoys friendly, if sometimes frank, bilateral relations is clearly unacceptable and requires a firm response," he said.
In Jerusalem, foreign ministry spokesman Yigal Palmor said the Israeli government regretted the Irish decision, which he said was "not in line with the importance of our relationship with the Irish government".
Forged British, French, Australian, and German passports were also used in the Dubai operation.
The UK and Australia have already expelled Israeli nationals over the forgeries.
Mr Martin said the Irish had co-operated closely with British and Australian authorities in their investigation of the killing.
He cited "the inescapable conclusion that an Israeli government agency was responsible for the misuse and, most likely, the manufacture of the forged Irish passports associated with the murder of Mr Mabhouh".
Irish authorities had asked for Israeli help in their investigation, he said, but such efforts had "yielded no response and no denial of Israeli involvement".
Six of the eight fake passports used the numbers of existing Irish passport holders, while the other two contained invented numbers conforming to the Irish format, the foreign ministry said.
Mr Martin said those whose passport numbers had been used had been issued with new passports and that he was confident this would allow them "to travel free from any suspicion".
"As I have stated from the outset, my priority throughout this affair has been to ensure the security of the innocent Irish citizens affected and to protect the integrity of the Irish passport," he said.
Last week it emerged that authorities in Poland arrested a suspected Israeli agent in connection with Mr Mabhouh's death.
Germany is seeking his extradition over a forged German passport used by one of the killers.