Donald Trump has said Iran will be hit “very hard” in the coming days, describing leaders of the regime as “deranged scumbags” who it was a “great honor” to kill, as Tehran residents reported relentless bombing and violence continued to spiral across the Middle East.

The US president’s comments, which signaled an intensification of the US-Israeli campaign, came as Israeli and US warplanes launched successive waves of attacks on the Iranian capital and elsewhere on Friday. One strike reportedly hit close to a square near Tehran University where crowds were gathered in support of Iran’s regime. The area is home to many government buildings.

Video published by the semi-official Tasnim news agency showed a plume of grey smoke rising as demonstrators screamed “Death to Israel!” and “Death to America!”

Across the region, there was more chaos, bloodshed and destruction, with further Israeli strikes in Lebanon, where 800,000 people have been displaced; new missile and drone attacks by Hezbollah and Iran on targets in Israel; and fresh Iranian attacks on civilian infrastructure in Gulf states.

The US said six servicemen were killed in an accident involving a tanker plane used for mid-air refuelling, which crashed in Iraq. Also in Iraq, a French soldier was killed in a drone strike by a pro-Iranian militia group.

In a post on social media, Trump wrote: “Watch what happens to these deranged scumbags today … They’ve been killing innocent people all over the world for 47 years, and now I, as the 47th President of the United States of America, am killing them. What a great honor it is to do so!”

Late on Friday, Trump said that US forces had “obliterated” military targets on Iran’s Kharg island and warned that the oil infrastructure there could be next. The small island is the primary terminal for Iran’s oil exports.

In a post on Truth Social, he said: “The United States Central Command executed one of the most powerful bombing raids in the History of the Middle East and totally obliterated every MILITARY target in Iran’s crown jewel, Kharg Island.”

He added: “I have chosen NOT to wipe out the Oil Infrastructure on the Island. However, should Iran, or anyone else, do anything to interfere with the Free and Safe Passage of Ships through the Strait of Hormuz, I will immediately reconsider this decision.”

Pete Hegseth, the US defence secretary, told a press conference in Washington earlier on Friday that Iranian leaders were “desperate and hiding, they’ve gone underground”.

Hegseth said Iran’s new supreme leader Mojtaba Khamenei, who issued a defiant statement on Thursday pledging to continue fighting, had been “wounded and likely disfigured”.

“He put out a statement yesterday – a weak one actually – but there was no voice and there was no video. It was a written statement. He called for unity … apparently killing tens of thousands of protesters is his kind of unity,” Hegseth said.

Iranian media published videos showing some of the members of the country’s regime at the demonstration in Tehran, including Ali Larijani, who heads the Supreme national security council, and Gholamhossein Mohseni-Ejei, the hardline cleric who heads the country’s judiciary. The foreign minister, Abbas Araghchi, was seen walking in the city’s streets.

Residents of Tehran said there had not been a “day without the explosions” since the war began with an Israeli strike that killed Ayatollah Ali Khamenei, Iran’s ruler for 37 years.

“The buildings are shaking … There’s rubble everywhere and people are still risking their lives to go to work,” a 66-year-old retired professor said. “Please stop this. I am begging the world to act now before the entire city is destroyed. I can’t leave the city, and have sick family members. Even those who want to flee, can’t. They are not giving us enough petrol to even drive far enough. We are trapped.”

A shopkeeper from the centre of Tehran said she had counted six explosions within the past hour.

“We’ve taped the windows with newspapers. I am hardly even sleeping. They have bombed all night. I am scared to step out. These are some powerful bombs because I don’t even hear the drones any more. That’s how continuous today’s explosions have been. It’s cold and the power keeps going off and on. We won’t have electricity soon I fear,” the 42-year-old said.

Israel had earlier announced another wave of strikes in Iran targeting infrastructure, and said its air force had hit more than 200 targets in the past 24 hours, including missile launchers, defence systems and weapons production sites.

Hegseth said that more than 15,000 “enemy targets” had been struck, which is more than 1,000 a day since the war began.

After steep drops on Thursday, stock markets rallied as oil prices fell slightly. About a fifth of the world’s oil and gas supplies travel through the narrow strait of Hormuz, which Iran has now in effect blocked by attacking shipping there.

The US is “dealing with” Iran’s attacks in the strait of Hormuz, Hegseth said, claiming Iran had not yet mined the crucial waterway.

The Financial Times reported that European countries, including France, have opened talks with Tehran seeking to negotiate a deal to guarantee safe passage for their ships through the strait, although Italy denied the report.

Iran has responded with daily attacks on oil and other infrastructure around the Gulf region, and on Friday, Saudi Arabia said that it had downed nearly 50 drones sent in multiple waves.

In Oman, two people were killed when two drones crashed in an industrial area in the region of Sohar, the Oman news agency reported.

A building at the Dubai International Financial Center sustained damage when hit with debris from what authorities described as a “successful interception”. DIFC is an economic free zone for banks, capital traders and wealth managers, home to exclusive restaurants and nightclubs.

Late on Friday, the Israeli military said it had launched a new wave of strikes on Tehran, and Qatar’s interior ministry issued evacuation orders for parts of Doha before explosions were heard in the centre of the city.

Qatar’s defence ministry subsequently said it had intercepted a missile attack.

Iran said earlier this week that it would target banks and financial institutions, after an airstrike hit a bank in Tehran, and the Revolutionary Guards announced on Friday that they had launched new salvoes of missiles and drones at Israel in coordination with Hezbollah, which has a close, decades-old relationship with Tehran.

The guards said in a statement that the operation was part of their annual al-Quds Day, which is intended to show support for the Palestinian cause.

In Lebanon, at least eight people were killed in an Israeli strike on the southern coastal city of Sidon, Lebanon’s health ministry said. Nine others were wounded, the ministry added.

Israel’s military also hit the Zrarieh Bridge, spanning Lebanon’s Litani River early on Friday, claiming it was being used by Hezbollah militants to move between Lebanon’s north and south. The military provided no evidence for the claim.

Israel Katz, the Israeli defence minister, said the strikes so far were “just the beginning” and that Lebanon’s government would “pay an increasing price for the damage to Lebanese national infrastructure used by Hezbollah”.

More than 600 people have been killed in Lebanon since the latest fighting between Israel and Hezbollah militants began, the health ministry said.

Iranian authorities say that more than 1,300 people have been killed in Iran, and Israel has reported 12 deaths. The US has lost at least 13 service members, while another eight have suffered severe injuries.

In northern Israel, nearly 60 people were wounded after Hezbollah said that it fired several rocket salvoes toward the area and at Israeli troops in southern Lebanon. Almost all the injuries were described as minor.