Israel has carried out heavy air strikes in Lebanon’s historic city of Baalbek in the eastern Bekaa Valley, after tens of thousands residents fled in response to evacuation orders issued by the Israeli military.

Mayor Mustafa al-Shell told the BBC that more than 20 strikes were reported in the Baalbek area, with five inside the city itself, where there is a Unesco-listed ancient Roman temple complex.

Lebanon’s state news agency said diesel tanks were also hit in the neighbouring town of Douris, where Mr Shell said pictures showed a huge column of black smoke rising into the air.

The Israeli military said it struck fuel depots belonging to Hezbollah in the Bekaa Valley, without giving details.

The attacks came as Hezbollah’s new secretary-general said the group would continue its war plan against Israel under his leadership and that it would not “cry out” for a ceasefire.

Speaking a day after his appointment was announced, Naim Qassem said he would follow the agenda of his predecessor, Hassan Nasrallah, who was killed in an Israeli air strike in Beirut last month.

Qassem made the speech from an undisclosed location amid reports suggesting he had fled to Iran, which is Hezbollah’s main supporter.

After weeks of an air offensive that has brought devastation to large parts of southern Lebanon and Beirut’s southern suburbs, the Israeli military appears to be expanding its campaign against Hezbollah in the east of the country – another area where the group has a strong presence and support.

Baalbek is a key population centre in the Bekaa Valley, near the border with Syria. It is a largely rural area and one of Lebanon’s poorest regions.

Hezbollah has established part of its infrastructure and recruited fighters from there.

The area is also strategically important for Hezbollah, as it is part of a route linking the group to its allies in Syria and Iraq and, ultimately, to Iran.

On Wednesday morning, the Israeli military issued evacuation orders for the whole of Baalbek and the neighbouring towns of Ain Bourday and Douris, warning that it would “act forcefully against Hezbollah interests”.

Roula Zeaiter, programme manager for the Lebanese Women Democratic Gathering (RDFL), said the orders sparked panic among residents, including displaced families from other parts of the country.

“Minutes after the order to leave came, the streets were filled with people grabbing their things, locking their homes and closing their shops,” she told the charity ActionAid.

“We’re scrambling like scared mice, moving from place to place. Lebanon is becoming like Gaza, with Israeli forces using the same tactics.”

Videos posted online showed huge traffic jams on the main roads out of the city.

Mustafa al-Shell estimated that about 50,000 people fled within two hours, but he added that many others decided to stay behind “for various reasons”.

He said the initial wave of Israeli strikes on Wednesday afternoon hit villas and other residential buildings in Baalbek’s city centre and its outskirts.

“It’s not clear what the Israelis have targeted,” he added. “But I can tell you that there are no ammunition dumps or weapons caches in Baalbek.”

The state-run National News Agency (NNA) reported that the Ras al-Ain Hills, Amshki, al-Asira, al-Kayyal Road areas were hit, and the northern and southern entrances to Baalbek. The strikes also targeted Ain Bourday and Douris, including diesel tanks in its vicinity, it said.

There were no immediate reports of any casualties, but the Lebanese health ministry did say that Israeli strikes killed 11 people in Sohmor, another town in the Bekaa Valley about 70km (43 miles) south of Baalbek.

The Israeli military said its aircraft conducted “intelligence-based strikes on fuel depots located inside military compounds belonging to Hezbollah’s Logistical Reinforcement Unit 4400 in the Bekaa Valley” on Wednesday.

“The unit is responsible for transferring weapons from Iran and its proxies to Hezbollah in Lebanon. These fuel depots supplied fuel for Hezbollah’s military vehicles and were critical to the operation of Hezbollah’s military infrastructure,” it added.

Mr Shell said none of the strikes hit Baalbek’s Unesco World Heritage site, which comprises the ruins of Roman temples which date back to the 1st Century AD and are among the largest and best-preserved in the world.

However, he warned of what he called “Israeli treachery” and said Lebanese authorities were “pleading… for international bodies to stand fast in defence of Baalbek’s Roman ruins”.

Unesco warned in a post on X on Wednesday that featured a photo of the Temple of Jupiter at Baalbek, that World Heritage sites across the Middle East, particularly those in Lebanon, were under threat.

“Unesco recalls to all parties their obligation to respect and protect the integrity of these sites. They are the heritage of all humanity and should never be targeted,” it said.

On Monday night, several buildings were levelled around the Gouraud Barracks area of Baalbek, near the Roman ruins, during Israeli strikes that killed more than 60 people across the Bekaa Valley.

When asked by reporters in Washington about the Baalbek strikes, US state department spokesman Matthew Miller said called on Israel not to threaten the lives of civilians or damage critical civilian infrastructure and cultural heritage.

He also confirmed that US Middle East envoys Amos Hochstein and Brett McGurk were “traveling to Israel to engage on issues including a diplomatic resolution in Lebanon, as well as how we get to an end to the conflict in Gaza”.

Two sources told Reuters news agency that US mediators were working on a proposal for a 60-day ceasefire between Israel and Hezbollah which would be used to finalise the full implementation of UN Security Council resolution 1701.

The resolution ended the last war they fought in 2006 and included a call for southern Lebanon to be free of any armed personnel or weapons other than those of the Lebanese state and a UN peacekeeping force.

Israel went on the offensive against Hezbollah – which it proscribes as a terrorist organisation – after almost a year of cross-border fighting sparked by the war in Gaza.

It says it wants to ensure the safe return of tens of thousands of residents of northern Israeli border areas displaced by rocket attacks, which Hezbollah launched in support of Palestinians the day after its ally Hamas’s deadly attack on Israel on 7 October 2023.

More than 2,800 people have been killed in Lebanon since then, including 2,100 in the past five weeks, and 1.2 million others displaced, according to Lebanese authorities.

Israeli authorities say more than 60 people have been killed in northern Israel and the occupied Golan Heights.