Israel, backed by the United States, and Iran on Wednesday threatened each other with retaliation if attacked as the United Nations Security Council met amid fears of a wider war in the Middle East.

"This deadly cycle of tit-for-tat violence must stop," UN Secretary-General Antonio Guterres told the 15-member council. "Time is running out."

The council met after Israel killed the leader of Lebanon's Hezbollah and began a ground assault against the Iran-backed militant group and Iran attacked Israel in a missile strike.

"Israel will defend itself. We will act. And let me assure you, the consequences Iran will face for their actions will be far greater than they could ever have imagined," Israel's UN Ambassador Danny Danon told the council.

Iran's UN Ambassador Amir Saied Iravani said the missile attack on Tuesday was "to restore balance and deterrence." He said further escalation could be avoided if Israel stopped the war in Gaza and attacks on Lebanon.

"Iran is fully prepared to take further defensive measures, if necessary, to protect its legitimate interests and defend its territorial integrity and sovereignty against any acts of military aggression and the illegal use of force," he said.

French UN Ambassador Nicolas de Riviere said France wants the Security Council to "show unity and to speak with one voice" to de-escalate the situation.

Israel and the United States both called for sanctions on Iran.

Guterres told the council he strongly condemned Iran's attack on Israel. Earlier on Wednesday, Israel's foreign minister said he was barring Guterres from entering the country because he had not done so.

Russia's UN Ambassador Vassily Nebenzia praised Iran for "exceptional" restraint in recent months and said the missile attack on Israel could not be "presented as though all of this happened in a vacuum, as though nothing is happening - and nothing did happen – in Lebanon and Gaza, in Syria, in Yemen."

"But it did happen, and it led to a new, very dangerous spiral of a widening Middle East conflict," Nebenzia said. (Reuters)