The hit squad that killed a senior Hamas official in Dubai may have entered the country using diplomatic passports, Emirates officials said yesterday as they called on the European countries whose documents were forged to launch a full inquiry.

“There is still information that Dubai police will not make public for the moment, especially regarding diplomatic passports,” said Lieutenant-General Dhahi Khalfan Tamim, Dubai’s police chief.

Authorities have issued international arrest warrants for 11 suspects in the case, but now believe that the team behind the murder numbered 17 at least. An insider close to the case said that the diplomatic passports were believed to have been used by as-yet-unnamed suspects, with the countries involved still to be identified.

The UAE’s Foreign Ministry yesterday summoned the ambassadors of all four EU nations whose documents were used. Edward Oakden, the British ambassador in Abu Dhabi, attended the meeting alongside his counterparts from Ireland, France and Germany. Anwar Gargash, the UAE minister of state for foreign affairs, said that his nation was “deeply concerned by the fact that passports of close allies, whose nationals enjoy preferential visa waivers, were illegally used to commit this crime”.

General Tamim said that the assassination of Mahmoud al-Mabhouh, a founder of Hamas’s armed wing whose death has been blamed on Israel’s spy agency, the Mossad, was “no longer a local issue but a security issue for European countries”.

His warning came after Mahmoud al-Zahar, a senior Hamas leader, hinted that while his militant organisation — which has carried out scores of suicide bombings — had restricted its operations to Israel in the past, complicity with Israel’s spy agency could lead it to reconsider the policy.

Officials close to the investigation said that at least two more suspects had entered the country on Irish passports. It also emerged that the German passport used by the killers was a real document that had been obtained fraudulently.

Der Spiegel magazine said that it had been issued in the name of Michael Bodenheimer, an Israeli-American whose Jewish parents fled Nazi Germany in the 1930s. The real Michael Bodenheimer, who was born in the United States and now heads a religious school in Tel Aviv, told the magazine that he had never applied for a German passport. The prosecutor’s office in Cologne has opened an investigation into the case.

In the latest twist in the complex affair, the Dubai police chief suggested that one of the slain Hamas leader’s own close associates may have leaked information on his whereabouts to his assassins, calling the unnamed mole “the real killer”.

Palestinian militant groups have often been infiltrated by Israeli intelligence in the past, and usually hand out death sentences to those caught collaborating with the Jewish state.

Hamas, in turn, said that Mr al-Mabhouh, believed to have been responsible for smuggling Iranian arms to the Gaza-based militants, was guilty of several security breaches, including booking his ticket on the internet and telling family members on the telephone of his movements.

“Al-Mabhouh called his family by phone before he travelled to Dubai and told them of his plan to stay in a specific hotel, and he booked his travel through the internet. This undoubtedly created a security breach,” said Salah Bardawil, a Hamas lawmaker.

Ayman Taha, a senior Hamas official, called on Dubai to form a joint investigative committee, something the emirate has so far refused. “We have very important information which has not so far been used,” he said. “We asked the Dubai authorities to be part of the investigation, but until now there has not been a positive response.”

The murdered militant’s brother denied Hamas’s accusation that he might have compromised his own safety. “I am the last one who received a call from Mahmoud,” said Fayek al-Mabhouh. “He didn’t tell me that he was going to Dubai and he never told any one of the family the details of his work or his movements.”

The accusations and countercharges came after suspicion fell on Hamas’s Palestinian rivals, Fatah, following the arrest by Dubai police of two former Fatah security officials from the Gaza Strip for alleged complicity in the hotel hit.