Dubai police widened Wednesday their search for the killers of a top Hamas militant in a luxury hotel, saying 15 new Western passport holders are suspects, bringing the total now sought to 26.

Six of the latest suspects wanted over the January 20 killing of Mahmud al-Mabhuh held passports from Britain, three from France, three from Ireland and the remaining three from Australia. Five women were among the 15 new names.

NONE Australia summoned its Israeli ambassador on Wednesday to explain how three Australian passports were used by the latest suspected killers, as Prime Minister Kevin Rudd vowed he would "not be silent on the matter."

The killing had already caused diplomatic tensions between Israel and four European countries -- Britain, Ireland, France and Germany -- whose fake passports were initially linked to the hit.

No government has directly accused Israel of being behind Mabhuh's murder but Dubai police chief Dahi Khalfan has said it is "most likely" the Israeli intelligence service Mossad was behind the crime.

"The new list of suspects includes people who offered prior logistical support and preparations to facilitate the crime, and others who played a central role," a police statement said.

Police said they were not ruling out the possibility that more people were involved as they were "still conducting a wide search and reviewing other links to the case."

All the new suspects bar one used credit cards issued by META Bank in the United States to book hotel rooms and pay for air travel, police said, adding that they came to Dubai from six different European cities and Hong Kong.

Israelis holding double nationality

In Israel, meanwhile, media said as many as 10 of the new suspects had used the identities of Israelis holding double nationality. Six Israelis with dual British citizenship have already been identified as suspects.

Dubai police initially released the names and photos of 11 suspects who had entered the UAE on European passports -- the six from Britain, three from Ireland, one from Germany and one from France.

NONE The emirate's police chief, Lieutenant General Dahi Khalfan, said last week that some of Mabhuh's killers used diplomatic passports.

These passports appear to have been falsified or stolen, and belonged to what appear to be ordinary citizens shocked to learn of their being linked to the case.

"Friendly nations who have been assisting in this investigation have indicated to the police in Dubai that the passports were issued in an illegal and fraudulent manner," said Wednesday's statement.

The United Arab Emirates condemned on Sunday the abuse of European passports by the assassins of Mabhuh, a founder of Hamas's armed wing.

"The abuse of passports poses a global threat, affecting both countries' national security as well as the personal security of travellers," Foreign Minister Sheikh Abdullah bin Zayed al-Nahayan said in a statement carried by the official WAM news agency.

Possible mole

Khalfan has called for Hamas to conduct an internal investigation into the killing, pointing to a possible mole in the Palestinian Islamist movement -- a theory Hamas rejects. It blames Israel and has vowed revenge.

According to Khalfan, two Palestinians have been arrested in Jordan and extradited to Dubai, where they are being held in connection with the murder.

Britain and Ireland said Wednesday they were contacting the latest passport holders implicated.

"We can confirm that six more UK passports have been identified, we will seek to make contact with these individuals and offer consular assistance as we have the previous individuals," the Foreign Office said in London.

"The foreign secretary and others have made clear we expect full Israeli co-operation."

In Dublin a foreign ministry spokesman said all the genuine Irish passport holders whose passport numbers had been used had been contacted.

-AFP