Israel’s military told residents of more than 20 towns in south Lebanon to evacuate their homes immediately on Thursday as it pressed on with its cross-border incursion and struck Hezbollah targets in a suburb of Beirut.

The latest warnings took the number of southern towns subject to evacuation calls to 70 and included the provincial capital Nabatieh, suggesting another Israeli military operation was imminent against the Iran-backed armed group.

Hezbollah also carried out new strikes, targeting what it called Israel’s “Sakhnin base” for military industries in Haifa Bay on the Mediterranean coast of northern Israel with a salvo of rockets.

Israel, which has been fighting Hamas in the Palestinian territory of Gaza for almost a year, sent troops into southern Lebanon on Tuesday after two weeks of intense airstrikes in a worsening conflict that has drawn in Iran and risks sucking in the US.

More than 1.2 million Lebanese have been displaced by Israeli attacks, and nearly 2,000 people have been killed since the start of the Israeli attacks on Lebanon over the last year, most of them in the past two weeks, Lebanese authorities said.

The World Health Organisation said 28 healthcare workers had been killed in Lebanon in the previous 24 hours. WHO chief Tedros Adhanom Ghebreyesus also said flight restrictions meant the agency would not be able to deliver a large planned shipment of trauma and medical supplies to Lebanon on Friday.

Rocket sirens wailed constantly in northern Israeli towns, sending residents running for shelter, as Hezbollah kept up its cross-border fire.

The Lebanese army said two soldiers were killed by Israeli strikes in separate incidents in south Lebanon on Thursday, one in an attack on a military post and another in a strike on a rescue mission with the Lebanese Red Cross.

The army said that it returned fire when the military post was struck, a rare development for a force that has historically stayed on the sidelines of major conflict with Israel.

In Beirut’s southern suburb known as Dahiye, a dense neighbourhood where Hezbollah holds sway, several explosions were heard on Thursday and several large plumes of smoke were rising after heavy Israeli strikes.

Hezbollah said it detonated a bomb against Israeli forces infiltrating a southern Lebanese village and attacked Israeli forces near the border.

Overnight, Israel bombed central Beirut in an attack the Lebanese health ministry said killed nine people.

A Hezbollah-linked civil defence group said seven of its staff, including two medics, were killed in the Beirut attack.

Israel also said it struck a municipality building in the southern Lebanese town of Bint Jbeil, killing 15 Hezbollah members and destroying many weapons.

As it pushes into Lebanon, Israel is also weighing its options for retaliation against its arch-foe Iran.

Iranian President Masoud Pezeshkian, speaking in Doha, said Tehran would be ready to respond and warned against “silence” in the face of Israel’s “warmongering”.

“Any type of military attack, terrorist act or crossing our red lines will be met with a decisive response by our armed forces,” he said.

The Lebanese border front opened after Hezbollah fired missiles at Israel on October 8 in support of Hamas in its war with Israel in Gaza.

More than 300 of the more than 1 million Lebanese displaced have taken shelter in a Beirut nightclub, once known for hosting glitzy parties and where staff are now using their guest-list clipboards to register residents. “We’re trying to keep strong,” said Gaelle Irani, who was formerly in charge of guest relations.