A car bomb in the Syrian capital, Damascus, has killed a senior member of Palestinian militant group Hamas.
Syrian officials said the vehicle was booby-trapped
Izz El-Deen Sheikh Khalil died after his booby-trapped car was completely destroyed in an explosion.
Hamas has accused the Israelis of being responsible for the killing and threatened to retaliate.
Syria also blamed Israel for the killing, which an official described as "a terrorist act" in comments reported by the state-run Sana news agency.
The assassination was intended "to shake security and stability in the region," the official said.
The Israelis had vowed to hit Hamas leaders "wherever they are" after suicide bomb attacks in August in Beersheba left 16 people dead.
"We blame Mossad (the Israeli intelligence service) for putting
a bomb in his car," Mushir al-Masri, a spokesman for Hamas told the AFP news agency in Gaza City.
Israel's Public Security Minister Gideon Ezra said he had no information about who was responsible.
"I can't confirm or deny it, (but) I'm not sorry this happened," he told Israeli television.
The BBC's Dale Gavlak, in Damascus, says there is tight security around the blast scene as police conduct their investigation.
She saw them remove the twisted wreckage of two cars.
Witnesses told her they saw Mr Khalil get into his car and answer his mobile phone moments before the vehicle blew up.
Three passers-by were injured.
Mr Khalil, aged 39, was a senior figure in the group's military wing and a member of the generation that founded the group.
He was based in Damascus along with other senior Hamas figures, including the overall leader, Khaled Meshaal.
He was among a group of around 400 Palestinian militants deported by Israel to Lebanon in the early 1990s.
Israel has killed dozens of Hamas militants, including the group's spiritual leader and his successor earlier this year.
The Israeli government also says it holds the Syrians responsible for the actions of Hamas and other Palestinian militant groups based in Damascus.
Syria insists its support is political and not military.
Last October, Israel carried out its first attack on Syrian soil for 30 years, targeting what it called a Palestinian terrorist camp near the Syrian capital.
This was in retaliation for a devastating suicide bomb in the northern port of Haifa which had killed 19 people.
Syria said the target was a refugee camp.
Syria and Israel have long been at loggerheads over the Golan Heights, which Damascus lost to Israel in the 1967 war.