Israel's prime minister defended a US decision to launch an air strike on Friday that killed powerful Iranian commander Qassem Soleimani and the Israeli military was put on high alert, after Iran threatened revenge.
Senior defence officials in Israel, America's closest ally in the Middle East and Iran's top regional foe, also met to assess the situation after the killing of Quds Force chief Soleimani and an Iraqi militia commander in the strike.
"Just as Israel has the right of self-defence, the United States has exactly the same right," Israeli Prime Minister Benjamin Netanyahu said in a statement issued by his office.
"Qassem Soleimani is responsible for the death of American citizens and many other innocent people. He was planning more such attacks," he said, speaking at an airport in Greece before heading back to Israel after cutting short his trip.
Israel's Army Radio said the military was on a heightened alert, and officials said Defence Minister Naftali Bennett met military and intelligence chiefs for a "situational assessment".
Israel has long regarded Soleimani as a major threat. The military said in August it had foiled a Quds Force attack, masterminded by Soleimani that involved multiple drones operating from Syria.
Netanyahu said in his statement on Soleimani's killing that US President Donald Trump "deserves all the credit for acting swiftly, forcefully and decisively. Israel stands with the United States in its just struggle for peace, security and self-defence."
Israel has also accused Soleimani of leading Quds Force efforts to establish a precision-guided missiles programme for Hezbollah, the Lebanese movement that is backed by Tehran.
Israel is concerned about retaliation from Iran's proxies and allies in the region, such as Hezbollah and Palestinian militant groups Hamas and Islamic Jihad in Gaza.
Yair Lapid, an Israeli opposition lawmaker, echoed Netanyahu's comments, congratulating Trump on Twitter for killing those responsible for "murderous terrorist acts from Damascus to Buenos Aires".
Israeli military spokesman Avichay Adraee said the Mount Hermon ski resort, which is in the Israeli-occupied Golan Heights lying close to the fortified frontier with Syria, had been closed "following an assessment of the situation".
"There are no further instructions to the residents of the Golan Heights area and routine activities continue as normal," Adraee added.
In Gaza, Hamas, which has long enjoyed financial and military support from Tehran, condemned Soleimani's killing and offered its "dearest condolences" to Iran.
Gaza-based Hamas official Bassem Naim wrote on Twitter that the assassination "opens the doors of the region to all possibilities, except calm & stability. USA bears the responsibility for that".
Iranian-backed Palestinian militant group Islamic Jihad, which is also based in Gaza, praised Soleimani as a leader "who always brought horror into the hearts of America and Israel".
"The alliance of resistance will not be defeated, will not be broken and its integrity will become stronger in confronting the Zionist-American project," Abu Hamza, a spokesman for Islamic Jihad, said on Twitter.