A Lebanese militant notorious for the 1979 murder of three Israelis, including a little girl, has been killed in an Israeli air raid near Syria's capital, his Hezbollah movement said.
Samir Kantar was freed by Israel as part of a prisoner swap in 2008, three decades after the killings, and he became a high-profile figure in Hezbollah.
Late Sunday, at least two rockets were fired into Israel from Hezbollah's south Lebanon heartland, security sources on both sides of the border said. No casualties were reported.
The Israeli military said it responded with "targeted artillery fire".
One rocket hit northern Israel's Galilee area, military sources said, adding that residents were ordered into bomb shelters.
In September, the United States placed Kantar on its terror blacklist, saying he had "played an operational role, with the assistance of Iran and Syria, in building up Hezbollah's terrorist infrastructure in the Golan Heights".
The 54-year-old was killed on Saturday night "when the Zionist enemy planes bombed the building where he lived in Jaramana", southeast of Damascus, the Shiite militant group said in a statement.
Syrian Prime Minister Wael Halaqi said targeting Kantar was equivalent to "targeting the axis of resistance", referring to Syria and its allies.
Iran, a close Damascus ally, called it an "assassination" and a "violation of an independent country's national sovereignty and territorial integrity".
The Britain-based Syrian Observatory for Human Rights monitoring group said Israeli aircraft had tried but failed several times in the past to hit Kantar inside Syria.
Israeli Justice Minister Ayelet Shaked said her country "has not claimed" the strike but "was happy to learn the news".
"He was an arch-terrorist who killed a young girl by fracturing her skull and had continued his terrorist activities after being freed," she told military radio.
"It's a good thing he met his maker."
The family of the Israeli victims said "justice has been done".
- Confetti and applause -
Kantar's brother Bassam confirmed the militant's death on Twitter, saying: "We are proud to have joined the long list of families of martyrs."
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Kantar and four other prisoners received a triumphant red carpet welcome in Lebanon in 2008 when they were exchanged for the bodies of two Israeli soldiers.
Wearing a Hezbollah military uniform, he waved to applauding crowds under a shower of confetti.
In an interview with AFP, Kantar said he was more than ever committed to wiping Israel off the map.
"The resistance will end only when the Zionist entity disappears," he vowed.
Former Israeli national security adviser Yaakov Amidror said on Sunday Kantar had been "very active in the north part of the Golan Heights in the Syrian side, responsible for preparing the area for attacks against Israel".
"And if he is neutralised by someone, it's good news for the state of Israel," said Amidror, but added that he did not know whether his country was behind his death.
- 'Justice has been done' -
Kantar, who had earned the title of longest-serving Arab prisoner in Israel, was still a teenager when he and three other members of the Palestine Liberation Front infiltrated the Israeli village of Nahariya by sea from Lebanon.
The militants shot dead Danny Haran, 28, and battered his four-year-old daughter Einat's skull with rifle butts in an attack that shocked Israel to the core.
Kantar was sentenced to five life terms plus 47 years for murdering the father and daughter and an Israeli policeman.
Haran's widow Smadar told army radio on Sunday that "justice has been done, especially when we know that he has continued to be active in terrorism against us since his release".
Their second daughter suffocated as Smadar tried to keep the two-year-old from making noise and revealing their hiding spot during the kidnapping of her husband and other daughter.
It is not the first time that Hezbollah, which has deployed thousands of men to fight alongside the Syrian regime in the country's conflict, has accused Israel of killing one of its senior figures in Syria.
In February 2008, top Hezbollah official Imad Moughnieh, wanted by Interpol over the 1992 car bombing of the Israeli embassy in Buenos Aires, was killed in Damascus. Israel denied responsibility.
In 2006, the militant group fought a month-long war with the Jewish state that devastated several parts of Lebanon.
That conflict killed more than 1,200 people in Lebanon, mostly civilians, and around 160 Israelis, most of them soldiers.