Pressure mounted Wednesday for Israel to respond to speculation that its Mossad spy agency killed a Hamas operative in a Dubai hotel last month, with Britain's prime minister promising to investigate the use of forged British passports by the alleged assassins and analysts in Israel taking unusual aim at the country's vaunted undercover organization.

Of the 11 members of the squad that Dubai authorities say carried out the killing of Hamas commander Mahmoud al-Mabhouh, six carried apparently fake British passports bearing the names of Israeli citizens. The British Foreign Office summoned the Israeli ambassador to a meeting over the matter Thursday, and Prime Minister Gordon Brown said a full inquiry will be mounted.

"The British passport is an important document that has got to be held with care," Brown said. "The evidence has got to be assembled about what has actually happened and how it happened and why it happened."

Police officials in Dubai have not ruled out Mossad involvement in Mabhouh's slaying, but they have not emphasized the possibility, either. Dubai, like the other small Persian Gulf states that make up the United Arab Emirates, does not have diplomatic ties with Israel, but it is also considered less hostile toward Israel than some other Arab countries.

In Israel, several prominent commentators engaged in surprisingly sharp criticism of an agency that in recent years has been credited with successes against militant groups such as Hamas and Hezbollah, as well as their patrons in Iran and Syria.

In the Haaretz daily, security affairs correspondent Amir Oren urged that Mossad head Meir Dagan be fired in the wake of an operation that had turned embarrassingly public -- Dubai police this week released security camera video of the suspects in Mabhouh's hotel and elsewhere. Others called for a commission of inquiry. Whether supportive or critical of the operation, virtually all commentators wrote from the assumption that the Mossad had been involved in it.

"Mabhouh was not an envoy of the Education Board of Gaza to Dubai. He was a top terrorist," former Mossad agent Gad Shimron said in an interview. "There is no doubt about the Israeli footprints in this. The question is whether those who planned it took in the possibility that the Dubai police would be very efficient."

Israel has a record of using foreign passports to conceal the movements of its undercover operatives and has run into diplomatic trouble with Canada, New Zealand, Britain and others over the practice. The Mossad agents who tried to assassinate Hamas leader Khaled Meshaal in Jordan in 1997, for example, carried Canadian documents.

The Dubai case has the added wrinkle that the names and some other data on the passports match those of Israeli citizens who immigrated here from Europe -- and who were shocked to find themselves mentioned in the material released by Dubai police.

That has left Israeli officials in a quandary, on the one hand trying to maintain the country's "policy of ambiguity" -- neither confirming nor denying its involvement in covert operations -- and on the other, having to explain how the names of some of its citizens ended up on forged documents cited in an international murder investigation.

In Israel's first official comments on the matter, Foreign Minister Avigdor Lieberman told Army Radio on Wednesday that despite the presence of the names, there is "no reason to think that it was the Israeli Mossad and not some other service or country up to some mischief."

Tzachi Hanegbi, chairman of the Israeli parliament's Foreign Affairs and Defense Committee, said there are no plans to try to unravel why Israelis' names appeared on the passports. If there is suspicion of identity theft or concern about implication in a murder, those involved should consult a lawyer, Hanegbi said.

"I don't think the government is going to have anything to do with it," he said.

Mabhouh, who was based in Damascus along with other Hamas exiles from the Gaza Strip, was a founding member of Hamas's military wing. He was linked to the kidnapping and killing of two Israeli soldiers in the late 1980s and more recently is thought to have been involved in supplying arms and money to Hamas militants in Gaza. Hamas has blamed Israel for his death but has not said why he was in Dubai.

In Gaza, a spokesman for Hamas's military wing announced that the group has formed a plan to avenge Mabhouh's death.