Police in Dubai claim a European hit squad assassinated a top Hamas official in the city last month.
Arrest warrants have been issued for 11 suspects - six British, three Irish, one French and one German - thought to be involved in the killing of Mahmoud al-Mabhouh in a hotel room in Dubai on 20 January.
However, the British and Irish governments say their passports are fake.
Ireland says the names and their passport numbers do not match anything issued by Ireland.
Britain says it believes the six British passports are also fakes.
Hamas has accused the Israeli intelligence organisation Mossad of carrying out the killing; Israel has refused to comment.