DUBAI, United Arab Emirates -- Dubai police directly accused Israel's Mossad spy agency of orchestrating the hit squad slaying of a Hamas commander as the number of suspects rose Thursday to 18.
Lt. Gen. Dahi Khalfan Tamim was quoted as saying he was "99 percent, if not 100 percent" certain that Mossad was behind last month's slaying of Mahmoud al-Mabhouh in a luxury hotel room in Dubai.
The comments -- which appeared on a newspaper website -- came as international pressure mounted for Israel to answer questions about possible links to the Jan. 19 killing.
The investigation also widened to the United States. Emirates authorities said the alleged killers used fraudulent passports to open credit cards accounts through U.S.-based banks, an official said.
"Our investigations reveal that Mossad is involved in the murder of al-Mabhouh," Tamim was quoted as saying by The National newspaper, which is owned by the government of Abu Dhabi.
He told another local paper, Dubai-based Gulf News, that: "All elements strongly indicate the involvement of the Mossad."
Tamim and other Dubai police officials could not be immediately reached for further comment. Israel government spokesman Mark Regev also had no comment.
The international fallout from the murder in a Dubai hotel room showed no signs of easing, with Britain and Ireland summoning Israeli ambassadors Thursday for talks about the case following allegations that European passports were used by the alleged team of assassins.
A UAE official, who has close knowledge of the investigation, said at least 18 people -- including two women -- are now suspected in what Dubai police describe as a highly coordinated operation to kill al-Mabhouh, one of the founders of Hamas' military wing.
Ten of the men and one woman were identified by Dubai police Monday as members of the group that traveled to Dubai on apparently fraudulent passports -- six from Britain, three from Ireland and one each from Germany and France.
Britain has said it will investigate how some of the suspects came to have British passports -- and how they might have been produced.
British Foreign Secretary David Miliband said one of the nation's top diplomats, Peter Ricketts, "explained the concern we have for British passport holders in Israel" during the meeting with Israeli Ambassador Ron Prosor.
"He made clear that we wanted to give Israel every opportunity to share with us what it knows about this incident, and we hope and expect that they will cooperate fully with the investigation," he said, adding he would raise the issue with Israel's foreign minister when they meet in Brussels in the coming days.
Prosor told journalists he was not able to add additional information to Britain's request.
Israel's ambassador to Ireland, Zion Evrony, said he had nothing useful to tell Ireland because he knew nothing confidential about the Dubai assassination.
Irish Foreign Minister Micheal Martin has said the three Irish passports did have valid numbers but were issued to people with different names than those made public by Dubai.
He said the Foreign Ministry had contacted two people with the same passport numbers and found they had not lost their passports or had any stolen. The assassins apparently had access to pre-2005 passports that lacked biometric information, Martin said.
Also linked to the slaying are two Palestinians in Dubai custody and five others, including one woman who was caught on video surveillance at the luxury hotel where al-Mabhouh's body was found Jan. 20, said the official, who spoke on condition of anonymity in line with standing policies.
The official gave no further details on the Palestinians or the five other suspects.
But the official said that some of the suspects used the false passports to open credit card accounts at U.S. banks, but also gave no additional information.
Although no definitive links have been found to the suspects, speculation increasingly pointed to Israel and the Mossad. Names released by Dubai matched seven people living in Israel.
"Israel never responds, never confirms and never denies," Foreign Minister Avigdor Lieberman said in Israel's first official comment on the affair on Wednesday, then added: "I don't know why we are assuming that Israel, or the Mossad, used those passports."
But that did little to stop speculation of Mossad involvement -- and a possible national embarrassment if proven true.
Some Israeli commentators compared the case to another Mossad disgrace during Netanyahu's previous term as prime minister, the failed attempt to kill Hamas leader Khaled Mashaal in 1997. Two Mossad agents posing as Canadian tourists were captured after injecting Mashaal with poison, and Israel was forced to send an antidote that saved Mashaal's life. Today Mashaal is Hamas' supreme leader.
The Mossad has been accused of identity theft before. New Zealand convicted and jailed two Israelis in 2005 for trying to fraudulently obtain New Zealand passports. But it would be the first time the Mossad has been suspected of using the identities of its own citizens.
At a Gaza rally of some 3,000 supporters on Wednesday, Hamas' military wing vowed revenge. Addressing the crowd by phone, Mashaal said the al-Mabhouh assassination "paves the way for capturing soldiers until we free all our prisoners from (Israeli) prisoners."
Israel's spy service has been suspected of carrying out assassinations for decades. Recent ones include Imad Mughniyeh, a top Hezbollah commander who was killed in 2008 by a bomb that ripped through his Pajero SUV in Damascus, Syria. Israel denied any role in the hit.
Tehran also blamed Israel for the death of a senior Iranian physics professor who was killed last month when a bomb-rigged motorcycle exploded. Israel did not comment.