Mr Mabhouh was electrocuted and then strangled, reports said
The Irish foreign minister is to meet his Israeli counterpart over the use of fake Irish passports by three of the alleged killers of a Hamas commander.
Dubai police believe 11 "agents with European passports" killed Palestinian militant Mahmoud al-Mabhouh in January.
The passports had real numbers, but the names on them did not correspond to those in the genuine passports.
Michael Martin said he would discuss the matter with Israeli Foreign Minister Avigdor Lieberman on Monday.
"I intend to meet the Israeli foreign minister in Brussels to underline our deep concern about the fake use of passports in Dubai and to seek reassurance and clarification on this very serious issue."
Speaking at an event in Cork, Mr Martin said he planned to further discuss the issue at his regular meeting with 26 other EU foreign ministers next week.
"I also spoke with the foreign minister of the United Arab Emirates overnight and we remain in close contact with the British government," he added.
Last Thursday, Irish officials met Israel's ambassador to discuss the use of the fake passports.
The ambassador, Dr Zion Evrony, said he had no information on the matter.