A notorious Lebanese militant leader, viewed by the United States and Israel as a terrorist and deeply involved in the Syrian civil war, was killed late Saturday in an airstrike on the outskirts of Damascus.

Suspicion for the attack, which killed Samir Kuntar and at least eight others affiliated with the Lebanese militant group Hezbollah, immediately fell on Israel. Kuntar was released by Israel in 2008 after he spent three decades in prison for his role in the killing of three Israelis, including a 4-year-old girl and her father.

Hezbollah, which is embroiled in the Syrian war in support of the regime, said it would take revenge on Israel for Kuntar’s death. A few hours later, three rockets were fired from southern Lebanon into northern Israel, sending residents in towns along the border into bomb shelters. There were no reports of casualties, and the Israeli military said it responded with targeted artillery fire at sites in southern Lebanon.

The Israeli military said in a statement that it “holds the Lebanese Army responsible for attacks emanating from its territory.”

In Lebanon, Hezbollah’s al-Manar TV station confirmed Kuntar’s death, reporting early Sunday that four Israeli missiles had struck a residential building in Jaramana, just outside Damascus, the Syrian capital.

Samir Kuntar in 2008, when he was released from Israeli prison. (Nabil Mounzer/European Pressphoto Agency)

Officials in Israel did not deny or confirm whether it was behind the hit.

Kuntar received three life sentences for his part in a deadly attack on April 22, 1979, in the northern Israeli town of Nahariya. Israel released him three decades later in exchange for the bodies of two Israeli soldiers captured by Hezbollah in 2006, an event that sparked a 33-day war with Israel.

Kuntar was 16 when he and three other militants entered Israel by boat from Lebanon in 1979. The cell killed a police officer before breaking into a home and taking Danny Haran and his daughter, Einat, hostage, later killing them, too.

On Sunday, Haran’s widow, Smadar Haran Kaiser, said she felt relief that Kuntar was dead.

“When I heard eight months ago that Samir Kuntar was active in Hezbollah in areas north of Israel, I started to worry that he might kill other families and children. I remember how brutal he was. I worried he might strike again,” she said in a call with journalists.

Haran Kaiser’s second daughter, Yael, 2, also died that day. The two had been hiding in a closet, and Haran Kaiser accidentally smothered her child as she tried to keep Kuntar from hearing the girl’s cries.

“If after he was released he’d gone to live a quiet life with his family in Lebanon, then I don’t think anyone would have the goal to kill him, but Samir Kuntar made many enemies, not just in Israel,” Haran Kaiser said.

Many Israeli leaders hailed the news of Kuntar’s death. Opposition leader Isaac Herzog tweeted that it was “historic justice.”

“He was a terrorist who refused to abandon the path of murder and terror. The region is safer without him,” Herzog wrote.

Energy Minister Yuval Steinitz said, “I will not refer to reports and rumors about the elimination of Hezbollah operative Kuntar, but if true, I would not be sorry. He was a villain.”

The attack comes as Hezbollah escalates its military operations in Syria as part of an offensive led by Russia that aims to bolster President Bashar al-Assad’s government as it battles a rebellion. In late September, Russia began airstrikes, which hit Syrian rebel groups.

Scores of Hezbollah militants have been killed in the offensive, along with soldiers and militiamen from Iran who also are part of the assault on Assad’s opposition. Iran and Russia are allies of Assad.

In the context of the complicated Syrian civil war, Yaakov Amidror, a former Israeli national security adviser, said it was not 100 percent certain that Israel was behind the Saturday attack, even though Israel had intelligence that Kuntar was pivotal in Hezbollah’s efforts to open a new front against Israel along its northern border with Syria.

“If he was neutralized by someone, then it is good news for Israel, but there are many people in Syria who have an interest to kill this guy because he worked so closely with Assad,” Amidror said.

The incident could complicate intensified diplomatic efforts to end the Syrian war and to defeat the Islamic State militant group, which controls parts of Syria and Iraq. In a rare sign of unity over the conflict, the U.N. Security Council approved a resolution Friday endorsing a peace process that involves negotiations between the Syrian government and the opposition to establish a transitional authority. The drafting of a new constitution and elections are expected within 18 months.

The plan is part of the “Vienna process,” which has received backing from opponents of Assad, including the United States and Saudi Arabia, and his Russian and Iranian allies. But the still-divisive issue of what to do with the Syrian leader during the transition has not been spelled out, and that could torpedo the entire diplomatic process.

The State Department deemed Kuntar a specially designated global terrorist in September for his role in the 1979 killings and his ties to Hezbollah, which the United States considers a terrorist organization. According to the department, Kuntar has played an operational role, with the assistance of Iran and Syria, in building Hezbollah’s terrorist infrastructure in the Golan Heights.

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