US President Donald Trump says only Iran's 'unconditional surrender' can end war

Tehran: President Donald Trump said Friday that only Iran's "unconditional surrender" would bring an end to the Middle East war, as Tehran was rocked by some of the heaviest US-Israeli strikes of the spiralling, week-long conflict.

Now in its seventh day, the war has embroiled nations beyond the region, upended the world's energy and transport sectors, and brought chaos to even usually peaceful areas around the Gulf.

It has spread to Lebanon, whose prime minister warned of an impending humanitarian disaster as tens of thousands fled heavy Israeli strikes on Beirut's southern suburbs.

Trump, who has given varying reasons for starting the war that killed Iran's supreme leader Ayatollah Ali Khamenei last weekend, promised to help rebuild the country's economy if Tehran installed an "acceptable" new leader.

"There will be no deal with Iran except UNCONDITIONAL SURRENDER," Trump wrote on his Truth Social platform.

"MAKE IRAN GREAT AGAIN (MIGA!)," he added.

In Tehran, crowds of men and women dressed in black, some carrying Iranian flags, gathered for the first Friday prayers since the start of the war, online footage showed.

Several loud explosions sent clouds of black smoke into Tehran's sky, according to AFP journalists who described the day's strikes as the heaviest yet on the capital.

"It's really very scary," a Tehran businessman who gave his first name as Robert told AFP.

"Checkpoints have been put up in place in the city to prevent looting and ensure control," the 60-year-old said at the Armenian border with Iran.

Both Israel and the US warned on Friday they were escalating their attacks on Iran.

"We have additional surprises ahead which I do not intend to disclose," Israel's military chief Lieutenant General Eyal Zamir said.

According to Iran's health ministry, the US and Israeli strikes on the country have killed 926 people.

Iranian government spokeswoman Fatemeh Mohajerani said on Friday that 30 per cent of the dead were children. AFP could not independently verify either toll.

Iran has launched missile and drone attacks at Israel and Gulf states since the war began, with AFP journalists in Tel Aviv reporting hearing several blasts on Friday.

In Israel, at least 10 people have been killed, according to first responders there.

The US military has reported the deaths of six of its personnel.

The conflict has sucked in Israel's neighbour Lebanon after Tehran's proxy group Hezbollah launched missiles at Israel.

Israeli air strikes hit sites in Lebanon's south and east on Friday.

There has been widespread destruction in the southern Beirut suburbs, considered a Hezbollah stronghold and home to an estimated 600,000 to 800,000 people.

AFP correspondents on the ground saw scenes of panic on Thursday as residents massively fled after an unprecedented Israeli order to evacuate immediately if they wanted to save their lives.

Hundreds of families milled around on a Beirut beach, left with nowhere to go.

"We'll sleep on the road tonight and God alone knows what will happen to us," one man told AFP, declining to give his name.

Lebanon's Prime Minister Nawaf Salam warned that a "humanitarian disaster is looming" from the displacement.

On Friday, Hezbollah told Israeli residents to evacuate areas within five kilometres (three miles) of the Lebanese border.

The death toll in Lebanon rose to 217 on Friday, according to the country's health ministry.

Israel's army meanwhile said it had killed more than 70 Hezbollah militants.