The initial nods, winks and pats on the back here over the assassination last month of a senior Hamas official in Dubai are turning to puzzlement and concern as mounting evidence, including extensive surveillance videos, points to a remarkably clumsy operation many Israelis deem unworthy of their intelligence service, Mossad.

Officially, Israel has neither confirmed nor denied involvement in the case, as is customary in delicate matters of intelligence and national security. But since the news of the assassination broke last month, Israel has unofficially made the story its own, with newspapers blaring congratulatory headlines and government ministers praising Mossad’s director.

However, then the Dubai police released images showing some of the 17 people suspected of being in the hit squad bumbling about in poor disguises, and Britain became infuriated by the use of faked British travel documents. Now Israelis are wondering whether their once-famed spy service could have been behind such a sloppy job or, in a John Le Carré-like twist, if Israel could have been framed.

On Wednesday, a commentator for the newspaper Haaretz, Amir Oren, wrote a front-page column about the case, calling for the Mossad chief, Meir Dagan, to step down.

“What must have seemed to its perpetrators as a huge success,” he wrote, “is now being overshadowed by enormous question marks.”

Israel wanted the Hamas official, Mahmoud al-Mabhouh, 50, for the capture and killing of two Israeli soldiers in 1989 and for smuggling weapons to Hamas in Gaza. On Jan. 19, he was killed in a Dubai hotel room.

On Monday, the Dubai police named 11 of the 17 people they suspect in the case. Among the names were those of three Irish citizens — of whom the Irish authorities have no record — and six British citizens living in Israel who appear to be victims of identity theft. The police also showed images culled from the ubiquitous closed-circuit TV system showing some of them in false beards, wigs and glasses, in almost comical attempts at disguise.

With the agents’ passport pictures now splashed across newspapers and television screens around the world, Israeli commentators said the agents, whoever they may really be, have been burned. Eitan Haber, a columnist in the daily newspaper Yediot Aharonot and a close aide to Prime Minister Yitzhak Rabin in the 1990s, wrote Wednesday, “They cannot even go to the grocery store.”

In a first official reaction, the foreign minister, Avigdor Lieberman, said Wednesday that Israel’s policy of “ambiguity” in such cases was “correct.”

“I don’t know why we are assuming that Israel, or the Mossad, used those passports,” Mr. Lieberman told Army Radio. “Israel never responds, never confirms and never denies.”

Three former senior Mossad officials contacted by a reporter on Wednesday refused to comment at all.

The British authorities said they believed the British passports the Dubai police had collected were “fraudulent.” Prime Minister Gordon Brown called for a full investigation.

The six British citizens living in Israel — who woke up on Tuesday to find their names linked with the assassination — do not resemble the agents’ photographs from the passports bearing their names. Among the Britons was a physiotherapist, a technical writer and a repairman who lives on a kibbutz.

The name of an American-born Israeli was used by another of the suspects, who carried a German passport. That person studies in a religious seminary near Tel Aviv.

Three of the British citizens gave interviews to the news media on Tuesday, expressing their shock and some fear. By Wednesday they appeared to have gone incommunicado and did not answer or return a reporter’s calls.

Mr. Oren, in his front-page column in Haaretz, anticipated a diplomatic crisis over the suspicions that Mossad had counterfeited British passports.

“It is as if Israeli governments had never apologized to London for using British documentation,” he wrote, “as if they had not promised solemnly, when passports of Her Majesty’s subjects were found in a certain phone booth, that this would never happen again.”