* Hamas official says Mahmoud al-Mabhouh killed on Jan. 20
* Dubai police do not rule out Mossad involvement
* Mabhouh could have been poisoned - Palestinian source
* Hamas still wants prisoner deal with Israel
(Recasts with Dubai police commander)
By Khaled Yacoub Oweis
DAMASCUS, Jan 29 The Palestinian Islamist group Hamas accused Israel on Friday of assassinating one of its top military commanders in a Dubai hotel, and the Dubai police chief said he could not rule out the involvement of Mossad.
Mahmoud al-Mabhouh, an Israeli target since engineering the capture of Israeli soldiers in the 1980s during a Palestinian uprising, was killed on Jan. 20, a Hamas official told Reuters in the Syrian capital Damascus.
"I cannot rule out the possibility of Mossad involvement in the assassination of Mabhouh," Dubai police chief Dhahi Khalfan Tamim told Al Jazeera television, referring to the Israeli intelligence agency.
He said he could not announce the nationalities of those involved.
Dubai police had earlier said that a "criminal gang" had been following the victim's movements before his arrival in the United Arab Emirates.
An official statement said most of the suspects had European passports and left the country after the killing.
The United Arab Emirates does not have a peace treaty with Israel but has hosted Israeli officials and does business with Israeli companies.
There was no immediate comment from Israel.
Hamas leader Khaled Meshaal made an impassioned speech to thousands of mourners at Mabhouh's funeral on Friday at the Palestinian refugee camp of Yarmouk outside Damascus. A green Hamas flag covered the body as it was lowered into the grave.
Meshaal described Mabhouh as a "great man" who fought the Israelis for 30 years.
"I say to you Zionists, do not rejoice. You killed him but his sons will fight you," he said. "God already took our leaders and loved ones, but resistance goes on. Palestine is a blessed land. It will not remain patient."
Mabhouh's death lengthens Hamas's list of what it describes as "martyrs", and is a setback for the group in its fight against the Jewish state.
Israel has killed dozens of leaders and military figures in Hamas, founded two decades ago as a religious resistance movement against Israeli occupation.
"I cannot reveal the circumstances (of the killing)," said Izzat al-Rishq, a member of Hamas's politburo.
Rishq said Mabhouh, 50, was an important member of the Izz el-Deen al-Qassam brigades, Hamas's military wing.
He said the brigades "will respond (against Israel) in the appropriate time and place", but added that Hamas would not let the killing derail efforts to arrange a prisoner exchange with Israel, which has run into difficulties.
Mabhouh, who was born in the Gaza Strip but had lived in Syria since 1989, was killed a day after he arrived in Dubai, Rishq said.
A Hamas source in Gaza said Mabhouh was an active commander "until the moment of his assassination". He did not elaborate.
Another Palestinian source said Mabhouh was found dead in his hotel room in Dubai. He had barricaded the door of his room with chairs, a standard precaution by a man who believed Israeli intelligence had been after him for 20 years.
"It seems that an autopsy was ordered and found traces of poison in his body. Mabhouh was also ill. Hamas controls the information on this," the source said. "He was one of their main military guys, although not a crucial figure," the source added.
Mabhouh's brother Fayek told Reuters in Gaza his brother was killed "by strangulation after receiving an electric shock" and that two people were involved in the killing.
Syria and Iran are the main backers of Hamas, which controls the Gaza Strip.
Rishq, who lives in exile in Damascus along with several of Hamas's main figures, said Mabhouh engineered the capture of two Israeli soldiers during the Palestinian uprising in the 1980s. The soldiers were later killed.
Mabhouh was imprisoned several times by Israeli forces, who also razed his home in Gaza, Rishq added.
The United States, which has started a rapprochement with Damascus, wants Syrian authorities to help neutralise Hamas as an armed force.
Syria, which is seeking peace with Israel, resisted U.S. pressure several years ago to expel the Hamas leadership. (Editing by Tim Pearce) (Additional reporting by Nidal al-Mughrabi and Cindy Johnston)