Damascus, Syria ? In a hit claimed by Israeli security officials, a senior Hamas operative was killed in a car bombing Sunday outside his house in Damascus, the first such killing of a leader of the Islamic militant group in Syria.

Izz Eldine Subhi Sheik Khalil, 42, died instantly in the explosion, which wounded three bystanders. Witnesses said he was speaking on his mobile phone as he put his white Mitsubishi SUV in reverse before it exploded about 10 yards from his home.

Analysts said the killing appeared designed as much to warn the Syrians as to keep Hamas off balance.

Syria called the killing “cowardly” and top Hamas leaders, already taking extraordinary security precautions, went deeper underground. The killing threatened to take the Palestinian-Israeli conflict to new levels, with conflicting remarks from Hamas on whether it too would begin targeting Israeli interests abroad.

Security officials in Jerusalem, speaking anonymously, acknowledged in-volvement, though the Israeli government issued no statement. It had been warning for weeks that members of the group would not be safe in Syria.

Israel’s ability to infiltrate the Hamas leadership in Damascus will likely further rattle the group after Israel killed Hamas founder Sheik Ahmed Yassin and his successor as Gaza leader, Abdel Aziz Rantisi, in missile strikes this year.

The Syrian Interior Ministry said in a terse statement carried by the official news agency, SANA, that Khalil had not engaged in any militant activity inside Syrian territory, and that authorities were investigating the explosion.

SANA later quoted an unidentified government official as saying “this terrorist operation constitutes a dangerous development for which Israel bears responsibility.”

The killing also was a clear warning to top Hamas officials, who have stayed largely out of sight since Sept. 2, when the group claimed responsibility for the Aug. 31 twin suicide bombing in southern Israel that killed 16 Israelis.

An official passes the remains of a vehicle that was blown up Sunday in Damascus. Israel claimed responsibility for the car bombing, which killed a top Hamas leader. Israeli security source said the bombing killed Izz Eldine Subhi Sheik Khalil. The death was also reported on a Hamas Web site.

A Hamas statement published on the group’s Web site said Israel “has opened a new door for the struggle by transferring the battle outside the land of Palestine,” hinting it might expand operations against the Jewish state to its interests outside Israel.

But a Hamas spokesman in Lebanon, Osama Hamdan, denied any decisions have been made.