Gaza's civil defense agency said that Israeli forces on Thursday killed at least 18 people, including 15 who had gathered near an aid distribution site in central Gaza.

Civil defence official Mohammad al-Mugghayyir told AFP that "18 people have been killed due to ongoing Israeli shelling on the Gaza Strip since dawn today, 15 of whom were waiting for aid", adding that the remaining three were killed by shelling near Gaza City.

Israel's defense minister said Thursday that Iran's supreme leader Ayatollah Ali Khamenei "can no longer be allowed to exist" after an Israeli hospital was hit during an Iranian missile attack.

"Khamenei openly declares that he wants Israel destroyed -- he personally gives the order to fire on hospitals. He considers the destruction of the state of Israel to be a goal," Israel Katz told journalists in Holon near Tel Aviv. "Such a man can no longer be allowed to exist."

Russian President Vladimir Putin and his Chinese counterpart Xi Jinping on Thursday strongly condemned Israeli attacks on Iran in a phone call, the Kremlin said, adding that both leaders called for a diplomatic solution to the conflict.

"Both sides adhere to identical approaches, strongly condemn Israel's actions," Kremlin aide Yuri Ushakov told reporters, adding that Moscow and Beijing believed the end to the hostilities "should be achieved exclusively by political and diplomatic means".

Iran’s foreign minister will meet with European counterparts in Geneva as an Israeli airstrike campaign continues to target his country, state media reported Thursday.

Foreign Minister Abbas Araghchi will travel to Geneva for the meetings Friday, the state-run IRNA news agency report.

U.S. President Donald Trump has told aides he has approved attack plans but is holding off to see if Iran will give up its nuclear program, the Wall Street Journal reported overnight.

He is due to receive an intelligence briefing on Thursday, a U.S. holiday, the White House said, while top U.S. diplomat Marco Rubio will meet his UK counterpart for talks expected to focus on the conflict.

Israel's defense minister overtly threatened Iran's supreme leader on Thursday after the latest missile barrage from Iran damaged a major hospital and hit a high-rise and several other residential buildings near Tel Aviv.

At least 40 people were wounded in the attacks, according to Israel's Magen David Adom rescue service. Black smoke rose from the Soroka Medical Center in the southern city of Beersheba as emergency teams evacuated patients. There were no serious injuries in the strike on the hospital.

President Donald Trump left the question of whether the United States will join Israeli strikes on Iran up in the air Wednesday, as he said that Tehran had reached out to seek negotiations.

"I may do it, I may not do it. I mean, nobody knows what I'm going to do," Trump told reporters as he supervised the installation of a new flagpole on the White House South Lawn.

Israel's military said it was striking military targets in Tehran on Wednesday, as AFP journalists reported hearing blasts in the north and east of the Iranian capital.

The Israeli air force "is currently striking military targets belonging to the Iranian Regime in Tehran," the military said in a statement, on the sixth day of the war between the arch foes.

As Israel pounds Iran with airstrikes targeting military facilities and its nuclear sites, officials in Tehran have proposed a variety of steps the Islamic Republic could take outside of launching retaliatory missile barrages.

Those proposals mirror those previously floated by Iran in confrontations with either Israel or the United States in the last few decades. They include disrupting maritime shipping through the Strait of Hormuz, potentially leaving the Nuclear Nonproliferation Treaty and attacks by allied militants.

Iran’s ambassador in Geneva derided as “hostile” and “unwarranted” U.S. President Donald Trump’s comments calling for Iran’s “unconditional surrender.”

Ambassador Ali Bahreini told reporters the Israeli campaign “has not been able to bring big damage to our nuclear facilities” because it had taken precautions to protect them.