But questions emerged about the list of suspects after Dubai authorities released pictures, names and passport photos identifying them as six Britons, three Irish and one each from France and Germany.

Ireland said the three alleged Irish citizens on the wanted list do not exist. In Germany, officials said the passport number given by Dubai for the lone German suspect is either incomplete or wrong.

Other elements also challenged the narrative presented by Dubai authorities, including how investigators pieced together the evidence pointing to an alleged European assassin team. Or why such an apparently well-planned operation would forget about the country's wide-ranging security cameras.

Hamas has repeatedly accused Israel's Mossad secret service of masterminding the slaying and has vowed revenge.

Al-Mabhouh, one of the founders of Hamas' military wings, had been wanted by Israel for his role in the 1989 kidnapping and killing of two Israeli soldiers on leave — something that was acknowledged by Hamas last month.

At least two Palestinians linked to the case were in the custody of Dubai authorities, leaving Hamas and its Palestinian rivals trading bitter accusations. The two men, both residents of the United Arab Emirates, had "fled to Jordan" after Al-Mabhouh’s murder, Dubai police chief Gen. Dhahi Khalfan Tamim said. The pair was extradited from Jordan "three days ago," Tamim said, adding there was "strong suspicion" that one of the two had met a member of the suspected hit team before the assassination.

Meanwhile, doubts were raised about some suspects' identities. Melvyn Adam Mildiner, 31, one of the men identified by the Dubai police as a suspect, was shocked when an AP reporter reached him on the phone in Israel and read him the information released by Dubai officials.

Mildiner, who said he holds a British and an Israeli passport, confirmed the name and the passport number matched his but said the date of birth was a few days off. He said he did not know how anybody obtained his UK passport, issued in 2001 and never reported lost. "I have my passport. It is in my house, along with the passports of everybody else in my family, and there's no Dubai stamps in it because I've never been to Dubai," he said.

Britain's Foreign Office said in a statement Tuesday that authorities were aware the “holders of six British passports have been named” as suspects in the case but added authorities believe the passports used were fraudulent.

Dubai officials have said they would press individual nations to hunt down the suspects.

— With input from agencies