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

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 (search) on whether it too would begin targeting Israeli interests abroad.

Security officials in Jerusalem, speaking anonymously, acknowledged involvement, 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 to 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 that "this terrorist operation constitutes a dangerous development for which Israel bears responsibility."

Ahmad Haj Ali, an adviser to the Syrian information minister, described the assassination as a "terrorist and cowardly action."

"This is not the first warning" Israel has tried to convey to Syria, Haj Ali said. "What happened indicates that Israel's aggression has no limits."

The killing, he said, "was meant to deliver a message to the entire world that says: 'We [Israelis] are capable of striking anywhere in accordance with the Israeli agenda.'"

Haitham Kilani, a Syrian political analyst, said the assassination was an "Israeli-American message" that Syria should take seriously. He predicted more assassinations if Syria "shelters and protects the Palestinian movements struggling against Israel."

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 bombing in southern Israel that killed 16 Israelis. Hamas has carried out numerous bombings and killed hundreds of Israelis. After the Beersheba attack Israel warned Syria that it was ultimately responsible for actions of the groups it sheltered.

Hamas leader Khaled Mashaal, who also has been based in Damascus, resurfaced in Cairo, Egypt, last week, where he again granted media interviews, spoke out against Israel and acknowledged taking extra security precautions. He was believed to have left Cairo, but would not say where he was going. Syria has denied evicting him from Damascus.

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.

"So far, there is no change in the policies of Hamas," he told The Associated Press in Beirut.

The group's militant wing in the Gaza Strip would decide on retaliation, which Hamdan said will come at the "appropriate time and place."

Police were seen recovering pieces of Khalil's body from the mangled and bloodstained car. Debris and broken glass were scattered at the site, which was sealed by police. Five other cars outside Khalil's home were damaged.

Khalil may have been targeted because he lived outside the well-guarded Yarmouk Palestinian refugee camp. His home was on the ground floor of the 10-story building in al-Zahraa, where he moved with his family about a year ago. The neighborhood is modest and densely populated, with residents living in towering apartments with shops on their ground floor and old, single-story stone houses.

On Friday, the London-based Al-Hayat newspaper reported that an Arab intelligence service had given Israel information on Hamas leaders abroad, including where they lived, what their hobbies were and even what food they ate. It cited unidentified Arab sources in Europe.

A member of the Hamas political bureau, Mohammed Nazzal, told The Associated Press in Cairo that Khalil worked for Hamas in the Gaza Strip until he was expelled by Israel in 1992.

Israel has killed many Hamas leaders in the West Bank and Gaza Strip, but Sunday's assassination in Damascus was the first of its kind outside the Palestinian territories. Israel tried to assassinate Mashaal in Jordan in 1997.

Sunday's action inside Syria was the first by Israel since October last year when Israel sent its warplanes to bomb a base of the Islamic Jihad, another Palestinian militant group that launches attacks against Israel targets. The air attack, the first in two decades, was retaliation for a Jihad bombing at a restaurant in Haifa where 19 people were killed.