LONDON (AFP) - Britain and Ireland said Tuesday that passports used by nine members of a suspected hit squad accused of assassinating a top Hamas commander in Dubai are fake. After the authorities in the Gulf said all 11 of those suspected of killing Mahmud al-Mabhuh last month held European passports, the governments in London and Dublin insisted their nationals were not involved. Hamas, the Palestinian movement which rules the Gaza Strip, has accused Israel of killing 50-year-old Mabhuh, who was found dead in his luxury hotel room, and vowed revenge. We are aware that the holders of six British passports have been named in this case. We believe the passports used were fraudulent and have begun our own investigation, said a spokesman for the Foreign Office in London. We have informed the authorities in the UAE (United Arab Emirates) that this is the case, and continue to cooperate closely with the Emiratis on this matter. On Tuesday, Dubai prosecutors issued an international arrest warrant against the 11, according to a statement. Irish authorities also said none of their nationals were involved. We have run the passport numbers and names through our system and there are no passports in those names or with those numbers, said an Irish Foreign Affairs Department spokesman. These purported passports are false. While there was no response from Germany, the French Foreign Ministry said it was not able to confirm the nationality of this person. To the best of our knowledge, we have not received an extradition request from the United Arab Emirates, said Christine Fages, a ministry spokeswoman. Michael Higgins, a lawmaker for Irelands opposition Labour Party, said the use of fraudulent Irish passport was of grave concern. It is not clear who was responsible for this killing, although local police in Dubai are not ruling out the involvement of the Israeli security services, Higgins said. In that light, it is now incumbent on the (Irish) minister for foreign affairs to seek assurances from the Israeli government that this is not the case.