Israel's military killed a commander for Palestinian Islamic Jihad in a strike on his home in the Gaza Strip early Tuesday, officials said, prompting retaliatory rocket fire.
Jihad's armed wing announced the death in a statement, after Israel confirmed it had targeted Baha Abu Al-Ata, 42, in a strike. The group said Ata's wife was also killed.
"Our inevitable retaliation will rock the Zionist entity," it said.
"A building in the Gaza Strip, in which the Palestinian Islamic Jihad senior leader Baha Abu Al-Ata stayed in, was attacked," Israel's military said in a statement, calling it a joint operation between the army and Israel's Shin Bet domestic security service.
Meanwhile, Syrian officials said an Israeli airstrike in the capital, Damascus, targeted another Jihad commander, Akram al-Ajouri, who was not harmed.
Syria's state-run news agency said Israeli warplanes fired three missiles at al-Ajouri's home, killing his son and granddaughter. The Israeli military had no comment.
Israel blamed Ata for recent rocket fire into its territory and said he was preparing further attacks.
The strike led to sporadic rocket fire from the Gaza Strip toward Israel, Gaza residents reported.
Hamas said Israel "bears full responsibility for all consequences of this escalation" and pledged that Ata’s death "will not go unpunished".
Israel said Ata was behind rocket fire toward a music festival in the Israeli city of Sderot in August as well as further rocket attacks at the start of November.
It has also blamed him for being behind sniper fire and drone launchings.
Ata "is responsible for most of the terror attacks in the last year from the Gaza Strip," the army said, describing him as a "ticking bomb".
It alleged he "was promoting preparations to commit immediate terror attacks in various ways towards Israeli civilians and (Israeli) troops during the recent few days."
The strike raised the possibility of a severe escalation between Israel and Palestinian factions in Gaza, which is ruled by Hamas and that is allied with the Jihad.
Three wars have been fought between them since 2008.
Israel's military said it had "deployed troops and is prepared for a wide range of offensive and defensive scenarios."
Lt. Col. Jonathan Conricus, a military spokesman, told reporters that Ata was responsible for several recent rocket attacks on southern Israel and that he was actively planning new attacks. "We essentially over the last week have been waiting for the opportune moment to conduct this surgical strike," he said.
Jihad gets its funding, weapons and guidance from Iran. It often carries out attacks independently of Hamas. Conricus described Ata as a powerful figure in Gaza who often acts alone without instruction even from Tehran.
Israel had no further plans to resume its assassinations of militant leaders — a practice that in the past has triggered heavy fighting. "There was no other choice," Conricus said.
The sudden surge in violence looked to awaken Israel's increasingly open conflict with Iran and its proxies in the region. Prime Minister Benjamin Netanyahu has issued a series of warnings recently about alleged Iranian aggression.
Netanyahu also has been criticized by southern border residents and political rivals for a tepid response to recent militant attacks. Netanyahu's Security Cabinet held a lengthy emergency meeting to discuss further action.
Netanyahu said afterward, speaking alongside military chief, Lt. Gen. Aviv Kochavi, that el-Ata, an "arch-terrorist, was the main generator of terrorism from the Gaza Strip."
"He was in the midst of plotting additional attacks these very days," Netanyahu said.
Just this week Netanyahu appointed hard-line politician Naftali Bennett as Israel's new defense minister to fortify his political base. Bennett has long advocated tougher action against Palestinian gunmen. But Bennett only formally took office Tuesday and the military said the operation had been planned long in advance.
Netanyahu said the cabinet approved the strike 10 days ago and waited for "a unique window of opportunity to carry out the operation in optimal conditions with maximum chances of success and minimum collateral damage."