Dubai will issue arrest warrants soon for 11 Europeans identified by police and suspected of the killing of a top Hamas commander.
It does not rule out Israeli involvement, the police chief said.
The 11 suspects include British, Irish, German and French passport holders, police chief Dahi Khalfan Tamim told reporters.
Hamas military official Mahmoud al-Mabhouh was found dead in a luxury Dubai hotel last month, and the Palestinian Islamist militant group has accused Israel of being behind the killing.
Israel has refused to comment but a security source there has said Mahmoud al-Mabhouh played a key role in smuggling Iranian-funded arms to militants in Gaza and Israel's media have been unanimous in linking Mabhouh to the Gaza arms supply.
A government source said six other people, not yet identified, were also suspected of involvement.
A leading suspect, who carried a French passport, had left Dubai for Munich via Qatar, Chief Tamim added.
‘We do not rule out (the Israeli intelligence agency) Mossad, but when we arrest those suspects we will know who masterminded it. (We have not) issued arrest warrants yet, but will do soon,’ he said, adding that one suspect was a woman.
‘Israel carries out a lot of assassinations in many countries, even in countries that it is allied to,’ Chief Tamim said, adding that Mahmoud al-Mabhouh may have been killed by electrocution.
Mossad is widely believed to have stepped up covert missions against Hamas, Lebanon's Hezbollah militia, and Iran's nuclear project. Among killings attributed to Mossad were that of Hezbollah commander Imad Moughniyeh in Damascus two years ago.
Mahmoud al-Mabhouh, who was born in Gaza but had lived in Syria since 1989, was killed a day after he arrived in Dubai.
A police statement said the killers had adopted disguises including wigs and hats, used an electronic device to enter Mr Mabhouh's hotel room and lay in wait for him.
Mr Mabhouh's killing was the third high profile murder in less than two years in the United Arab Emirates.
‘The United Arab Emirates does not accept that its territory be used as an arena for settling scores, whatever their nature or cause or whatever the affiliation of those involved,’ the police chief said in a statement. ‘The Emirates is a country of justice and rule of law.’