An Israeli strike on Syria killed at least five people on Friday, Syrian state television said, with Israel alleging they were Iran-backed militants who fired rockets across the border.
Friday's air raid followed more than a dozen Israeli strikes on Thursday night which killed one person and wounded seven, a Syrian military source said.
Israeli Defence Minister Moshe Yaalon said Friday's raid hit members of a unit which on Thursday fired four rockets into northern Israel's Galilee region and the Israeli-occupied zone of the Golan, in attacks that did not cause any casualties.
"Elimination of the squad which fired at Israel yesterday is further proof that we shall not tolerate any attempt to disrupt the lives of Israeli citizens or harm their security," he said in a statement.
"Those who want to do so should know that the Israeli military and security forces will pursue them to the end and get our hands on them, anytime and anywhere."
Israeli Prime Minister Benjamin Netanyahu said that it was his government's policy to "hurt anybody who tries to hurt us".
"We have no wish to escalate events but we are sticking by our policy," he said in a statement.
"The Israel Defence Forces hit the squad that carried out the fire and the Syrian forces which allowed it."
An Israeli military source said that Friday's strike killed "four or five men" who he said were members of the Palestinian Islamic Jihad operating in Syria.
Syrian state TV however described the five killed as unarmed civilians, while the Syrian Observatory for Human Rights, a British-based monitoring group, said they were members of the pro-regime National Defence Forces.
Israel earlier said that it hit 14 Syrian army positions in the Syrian-controlled sector of the Golan Heights on Thursday night in response to the rocket attacks.
Previous cross-border fire has frequently been attributed to spillover from fighting inside Syria and to Islamist rebels holding ground close to the Israeli-held sector of the strategic Golan.
There has not been rocket fire from Syria at the Galilee for a long time, perhaps since the 1973 Yom Kippur War, Israeli media reported, and analysts said it was a potential game-changer.
"The message is clear: this is a new front, a new battleground," Eyal Zisser of Tel Aviv University told AFP.
"The assumption is that they want to send the message that a new front is open now that the situation on the ground is changing," said Shlomo Mofaz, of the International Institute for Counter-Terrorism, near Tel Aviv.
Yaalon, in an earlier statement, said Thursday's attack on Israel was launched from positions under the control of President Bashar al-Assad's forces.
"The fire was carried out from territory controlled by the Assad regime, which allows terrorist activity against Israel and which we hold as also responsible," he said.
He said the actual assault was "carried out by a terrorist cell of Islamic Jihad, operated, funded and armed by Iran."
Iran is one of Assad's main backers and a supporter of the Palestinian Islamic Jihad. The militant group has its headquarters in Damascus.
Israel's foreign ministry said on Friday that the Islamic Jihad force which carried out Thursday's rocket fire was under the operational command of an officer of the Iranian Revolutionary Guards Corps.
"We have credible information that the attack was carried out by the Palestinian Islamic Jihad organisation and was facilitated and directed by an Iranian operative, Saaed Izaadhi," ministry spokesman Emmanuel Nahshon said in a statement.
He said that Izaadhi headed a Palestinian unit in the Revolutionary Guards' elite Quds Force.
Israel seized 1,200 square kilometres (460 square miles) of the Golan from neighbouring Syria in the 1967 Middle East war and annexed it 14 years later, in a move never recognised by the international community.