Hamas has claimed that one of its commanders was assassinated by Israeli agents in Dubai.
A statement by the Palestinian group, which controls the Gaza Strip, alleged on Friday that Israel had killed Mahmoud Abdul Raouf al-Mabhouh.
"I cannot reveal the circumstances. We are working with the authorities in the United Arab Emirates," Izzat al-Rishq, a Hamas official, was quoted by the Reuters news agency as saying.
But a brother of al-Mabhouh said he had been killed by electric shock after an electrical appliance was held to his head.
"The first results of a joint investigation by Hamas and the [United Arab] Emirates show he was killed by an electrical appliance that was held to his head," Fayed al-Mabhuh told AFP by telephone.
"Material was sent to a Paris laboratory which confirmed he was killed by electric shock."
Al-Mabhouh, who was born in the Gaza Strip but who had been living in Syria since 1989, was allegedly assassinated a day after he arrived in Dubai.
Israeli officials have so far offered no comment on the incident.
'Important' member
Al-Mabhouh's body arrived in Damascus on Thursday, where he is due to be buried.
Rula Amin, Al Jazeera's correspondent in Lebanon, said: "It seems that Hamas has decided to reveal this incident [Al-Mabhouh's alleged killing] about ten days after it happened - it took place on January 20. Why they only decided to talk about it now, we still don't know."
Al-Mabhouh is said to have engineered the capture of two Israeli soldiers during a Palestinian uprising in the 1980s and was imprisoned several times by Israeli forces. Israel razed his home in Gaza.
Hamas has said he was an "important" member of Izz al-Din al-Qassam brigades, Hamas's military wing named after a Syrian religious leader who fought British colonial forces in Palestine in the 1930s.
-- with input from agencies
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