Iran warned Israel on Tuesday of a "firm and appropriate" response if it continued attacking targets in Syria, where Tehran has backed President Bashar Assad and his forces in their nearly eight-year war against rebels and militants.
Israel, which views Iran as its biggest security threat, has repeatedly attacked Iranian targets and those of allied militia in Syria. With an election looming in April, Israel has been increasingly open about carrying out its air strikes.
In a meeting with Syria's Foreign Minister Walid Moalem in Tehran, the secretary of Iran's National Security Council Ali Shamkhani said the Israeli attacks violated Syria's territorial integrity and were "unacceptable."
"If these actions continue, we will activate some calculated measures as a deterrent and as a firm and appropriate response to teach a lesson to the criminal and lying rulers of Israel," Shamkhani was quoted as saying by Fars news agency.
Prime Minister Benjamin Netanyahu said in January that Israeli forces would continue to attack Iranians in Syria and warned them to "get out of there" fast.
Syria's Moalem was quoted on Tuesday by a media unit run by Iran's Lebanese proxy Hezbollah as saying: "The Syrian government considers it to be its duty to keep Iranian security forces in Syrian territory."
Last month, Russia demanded that Israel end its "arbitrary" airstrikes on targets in Syria, two days after the Israeli Air Force struck a series of Iranian military and intelligence targets in response to a rocket strike on the Golan Heights.
"The practice of arbitrary strikes on the territory of a sovereign state, in this case, we are talking about Syria, should be ruled out," Russian Foreign Ministry spokeswoman Maria Zakharova said, in answer to a question from Russian news agency TASS about recent Israeli air strikes on Syria.
Israel recently ended its long-standing policy of ambiguity regarding strikes on Syria, with both Netanyahu and then-IDF chief of staff Gadi Eisenkot confirming that the Israeli airforce had carried out hundreds of sorties in its war-torn neighbor, with the intent of both halting weapons deliveries to Hezbollah in Lebanon and an Iranian entrenchment in Syria.
"We have a permanent policy: To strike at the Iranian entrenchment in Syria and hurt whoever tries to hurt us. This policy does not change whether I am in Israel or on an historic visit to Chad. This policy is permanent," Netanyahu repeated last month during a visit to Chad.
"We'll not accept Iranian entrenchment in Syria, which is meant to harm us and we are acting to eradicate it. US President Donald Trump's decision to pull out from Syria doesn't change our policy. Our red lines remain the same—in Syria and everywhere else," he said.
"Israel is operating against the Iranian entrenchment in Syria," the prime minister told new pilots at a recent Israel Air Force graduation ceremony.
Ynet correspondents contributed to this report