TEL AVIV— The mysterious assassination of an Arab terrorist who topped America and Israel’s "Most Wanted" lists for a quarter century is being cheered in Jerusalem and WashingtonImad Mughniyeh, the long-standing terrorist leader of Hezbollah, was killed by a car bomb in Damascus on Tuesday night. Such was the depth of secrecy around his movements that it took the Lebanese Shi’ite militia 12 hours to publicly identify him as the sole fatality.

Israeli military experts said Hezbollah’s "chief of staff" had been eliminated, dealing the militia a strategic blow. Hezbollah, like its Iranian sponsors, blamed Israel’s spy services for the killing and many Lebanese called for revenge.

Israeli embassies and airlines were put on high security alert, and the military’s deployment along the Lebanon border was boosted as a precaution.

Israeli Prime Minister Ehud Olmert, perhaps wary of sparking a new flareup less than two years after the Lebanon war, issued an unusual denial.

"Israel rejects the attempt by terrorist elements to ascribe to it any involvement whatsoever in this incident," his office said in a statement.

But political reporters said Olmert appeared elated in public after news of Mughniyeh’s death arrived. Some suggested the Israeli prime minister was glad to have the public think his administration, after being censured for the faulty handling of the 2006 Lebanon war, finally had hit Hezbollah hard.

The consensus among Israeli commentators was that the Mossad likely was behind the assassination, though some suggested the United States might have been involved as part of a goodwill gesture by Olmert toward President Bush.

Channel 10 television commentator Ofer Shelah said that if the Mughniyeh killing was Israel’s work, it might have served as an "elegant" answer to the July 12, 2006 kidnapping of two Israeli soldiers by Hezbollah — rather than the offensive Olmert ordered at the time, which turned into the 34-day Second Lebanon War.

But Shelah also warned Israelis against gloating, given that Hezbollah blamed Israel for the killing and promised to avenge it.

"Today, Hezbollah and the Islamic Resistance are ready to confront any possible Israeli aggression on Lebanon,” Hezbollah leader Sheik Hassan Nasrallah said Thursday at Mughniyeh’s funeral in Beirut, which was attended by more than 10,000 people, according to the New York Times. “You killed Imad outside the battleground. Our battle was inside the Lebanese territory. You crossed the borders. Zionists, if you wanted open war, let it be an open war anywhere.”

In response, the U.S. Department of Homeland Security issued a warning that was relayed to Jewish institutions in the United States.

Jerusalem sources said Israel’s new security alert could be in place for weeks or even months, given assessments that Hezbollah, still reeling from Israel’s offensive against it in the 2006 Lebanon war, would bide its time before launching a revenge strike.

Was killing Mughniyeh, Shelah asked, "worth Hezbollah’s revenge?"

There was little doubt over the 45-year-old fugitive’s guilt.

Mughniyeh was the mastermind behind a slew of Hezbollah attacks, from southern Lebanon to Buenos Aires, the Argentinean capital where the bombings of the Israeli Embassy in 1992 and the AMIA Jewish community center in 1994 killed scores of people.

Mughniyeh was named in connection with Hezbollah’s abduction of Israeli soldiers in 2000 and 2006, and even in the disappearance of Ron Arad, an Israeli airman who bailed out over Lebanon in 1986 and was subsequently captured and whose fate is still unknown.

"For us, Mughniyeh was on the level of Osama bin Laden in terms of the threat he posed,” Israeli analyst Ehud Yaari said. “It is impossible to overstate the blow that his death dealt to Hezbollah.”

Israeli Environment Minister Gideon Ezra said whoever killed Mughniyeh "should be congratulated.”

Mughniyeh was no less a target for the United States, featuring high on the FBI’s wanted list. He was believed to be behind the 1983 bombing of the U.S. Marines barracks in Beirut, which killed 241 U.S. service members, and the 1985 hijacking of a TWA airliner.

“The world is a better place without this man in it. He was a cold-blooded killer, a mass murderer and a terrorist responsible for countless innocent lives lost,” State Department spokesman Sean McCormack said. “One way or another, he was brought to justice.”

Israeli intelligence buffs marveled at the skill that must have been required to pull off such a surgical strike in a vigilant place like the Syrian capital.

But some pundits were circumspect about the impact on future Hezbollah activity.

"Military activity — and Mughniyeh was one of its pillars — is not, in contrast to what is thought in Israel, Hezbollah’s main role in the view of its followers,” Jacky Hugi, Arab Affairs correspondent for Israel’s daily Ma’ariv, said.

“In the ongoing battle between Israel and Hezbollah, Imad Mughniyeh’s elimination will change almost nothing. His place will be taken by someone else, either more talented or less, but the ideology will remain as it was.”