Israel is coming under increasing pressure over the assassination of a senior Hamas commander at a luxury Dubai hotel last month.
The Israeli ambassador in London was questioned by UK government officials on Thursday over the use of six "fake" British passports used by the hit team that allegedly killed Mahmoud al-Mabhouh.
Authorities in Ireland have also summoned the Israeli ambassador in Dublin after three Irish passports were also found to have been used in the operation.
Seven of the names used in the passports are thought to be stolen identities of people currently living in Israel.
The website of the Abu Dhabi government-owned daily The National on Thursday quoted Dahi Khalfan Tamim, the head of the Dubai police force, as saying that the investigation into the killing "reveal[s] that Mossad [Israel's security service] is involved in the murder".
Tamim said it "is 99 per cent, if not 100 per cent, that Mossad is standing behind the murder".
The police chief also told Al-Bayan, another Dubai publication, that the European passports used in the operation were not fakes and that Dubai immigration officers were "trained" by European security experts to spot such documents.
"This training qualifies immigration officers to spot fake passports," he said.
"They applied these procedures at Dubai airport when the alleged [killers] entered the country.
"No forgery was found in those passports."
'Policy of ambiguity'
Dubai police on Tuesday released closed-circuit television footage of 17 individuals believed to have been involved in the killing of al-Mabhouh's at the Al-Bustan hotel.
Eleven of the suspects were named based on immigration records, although all are believed to have entered the emirate on forged passports- including a French and a German passport, in addition to those from the UK and Ireland.
Britain's foreign ministry said the country's Serious Organised Crime Agency would lead an investigation into the matter in close co-operation with the Emirati authorities.
It said the UK would also provide support to its nationals "who have been affected by this fraudulent activity".
Israeli silence on the killing was broken on Wednesday by Avigdor Lieberman, the country's foreign minister, who said that "there is no reason to think that it was the Israeli Mossad, and not some other intelligence service or country up to some mischief".
However, he also said that Israel maintains a "policy of ambiguity" on intelligence matters.
In the Gaza Strip, the Palestinian territory run by Hamas, anger spilled onto the streets on Wednesday with thousands of people gathering at a rally vowing to avengethe death of al-Mabhouh.
Al-Mabhouh was a senior commander and one of the founders of the Ezzedine al-Qassam Brigades, Hamas'armed wing.
Khaled Meshaal, Hamas' leader and himself a victim of an attempted Israeli assassination, pointed the finger of blame squarely at Mossad.
"The time for promises and talk of revenge is done. Now is the time for action," he said, addressing the Gaza rally via video from Damascus, where he is based.
Strategic Forecasting, or Statfor, a US-based non-governmental intelligence company, released its analysis of the Dubai tapes on Thursday, saying the suspected assassins operated in a way that was "calculated, well-choreographed and, most of all, indicative of a professional operation".
"The tactics and logistics involved in this operation were well beyond the capabilities of known terrorist organisations and all but a few national intelligence services"
Excerpt from Strategic Forecasting, Inc report
"The tactics and logistics involved in this operation were well beyond the capabilities of known terrorist organisations and all but a few national intelligence services," the report(subscription only)
Stratfor said the tapes, however, did not offer clues as to which specific agency carried out the attack.
Despite this, the AP news agency reports that some Israeli security officials are convinced Mossad was behind the operation- both because of the possible motives for the killing and the use of Israeli citizens' identities.
Israeli media has seen mixed reactions, with some praising al-Mabhouh's death, and others criticising a sloppy operation.
A front-page commentary in the daily newspaper Haaretz called for Meir Dagan, the head of Mossad, to be removed from office.
But a source close to Dagan told the Reuters news agency that the intelligence chief has no intention to resignbefore the end of his term later this year.
For Dagan to resign on the heels of a political row over al-Mabhouh's death would be to admit having had a role in it, the source said.
Meanwhile, the diplomatic spat looks set to intensify, with calls in Britain for Ron Prosor, the Israeli ambassador, to be expelled if he fails to provide adequate answers.