Dubai police say they are "99% if not 100%" certain that Mossad was behind the execution of Hamas leader Mahmoud al-Mabhouh. There has been no official confirmation or denial from Israel. But officials in Jerusalem are said to have indicated to their US counterparts that the assassination, and the use of false Western passports by the hit squad, has raised concern among other "friendly services".

The sources say that some senior Israeli officials have suggested the operation is being viewed as "flawed" and "amateurish", given the fact that the Emirates police and intelligence service, who are not regarded as among the elite in the field, have been able to put together a detailed picture of what happened, and point the finger directly at Israel after agents allowed themselves to be captured in CCTV footage and left a trail of documentation.

In most cases in the past, Mossad had been able to cover its tracks after carrying out successful overseas assassination missions, giving it deniability even when all the indications were that the service was responsible. "On this occasion that is not the case, there were too many loose ends left behind," said a US official. "The way it was done was certainly dramatic, with a large cast. But in the security world these things, if they have to be done, are done with as little drama as possible."

The British Foreign Office angrily denied that Britain had been tipped off by Israeli agents before the killing of the Hamas commander in a luxury Dubai hotel by a team which included assassins using UK and Irish passports.

The British government insisted that it only knew about the role of the passports just hours before it was revealed in a news conference held by the Dubai police last Monday. It has offered new passports to six dual Israeli-British nationals whose names appeared on the "fraudulent" passports on which the assassins travelled. The latest moves came as European and US security sources suggested that serious questions were being raised inside and outside the Israeli intelligence services after what is being increasingly regarded as the "hugely problematic" con­- sequences of the assassination of Mahmoud.

Reacting to a report that the British government had had a tip off "very, very briefly" before the assassination last month, the FCO declared: "Any suggestion that we knew anything about the murder in Dubai before it happened, including about the misuse of British passports, is completely untrue."

The statement added: "As we have said already, the Dubai authorities told us about the role of British passports on 15 February, several hours before their press conference. We told them the following day that the passports used were fraudulent. The head of the Dubai police has also made clear that embassies were not contacted until shortly before the identity of the suspects was revealed."

Meanwhile the British embassy in Tel Aviv said that consular staff had contacted five of the six British passport holders living in Israel whose identities were used to offer them new documents. It said the purpose was to prevent their inadvertent arrest because of the alert by Interpol, which has circulated details of those wanted in connected with the hotel slaying.

Embassy spokesman Raffi Shamir said that staff had reached all the affected British passport holders except one, Melvyn Adam Mildiner. Earlier last week, shortly after it was revealed his identity had been used, Mildiner expressed shock and anxiety.

With debate about the Dubai operation still prominent in the Israeli media, some commentators have reported that Israel is confident that the operation will not cause a protracted diplomatic row. But one veteran mainstream commentator Yoel Marcus in Ha'aretz questioned whether the operation was itself wise, adding: "On the assumption that every victim of assassination has a replacement, is the assassination worth the revenge, which is sometimes very cruel?"