Lebanon’s health minister has said what is happening in his country is “carnage”, as hospitals struggle to cope with the number of casualties from two days of widespread Israeli air strikes targeting the armed group Hezbollah.

Dr Firass Abiad told the BBC it was “clear” that many of the 550 people killed in Monday’s attacks were civilians, including children and women.

Israel said it hit hundreds of Hezbollah sites, accusing the group of hiding weapons in residential areas.

On Tuesday, the Israeli military said it had killed the head of Hezbollah’s rocket forces as the strikes continued, while Prime Minister Benjamin Netanyahu said the group was leading Lebanon “to the edge of the abyss”.

Hezbollah responded by firing more than 300 rockets into northern Israel, injuring six people, according to the military.

Although neither side seemed interested in backing down, US President Joe Biden told the UN General Assembly that a full-scale conflict was “not in anyone’s interest” and insisted that a “diplomatic solution is still possible”.

UN Secretary General António Guterres warned that the world “cannot afford Lebanon to become another Gaza”.

Nearly a year of cross-border fighting between Israel and Hezbollah sparked by the war in Gaza has killed hundreds of people, most of them Hezbollah fighters, and displaced tens of thousands on both sides of the frontier.

Hezbollah has said it is acting in support of Hamas and will not stop until there is a ceasefire in Gaza. Both groups are backed by Iran and proscribed as terrorist organisations by Israel, the UK and other countries.

Monday’s Israeli air strikes across southern Lebanon and the eastern Bekaa Valley had resulted in the deadliest day in the country since at least 2006 – the last time Hezbollah and Israel fought a war.

Abiad told a news conference on Tuesday that 50 children, 94 women and a number of medical workers were among the 558 people killed. More than 50 hospitals were currently treating the 1,835 other people who were wounded, he added.

Later, in an interview with the BBC, the health minister described what happened as “carnage.”

“If you look at the people who were brought to the emergency rooms it’s clear that they’re civilians. They are not the combatants that the Israelis claim they are,” he said.

“We know about the victims of the attacks because our ambulances are the ones that transferred them to hospitals,” he added. “[They were] civilians who were doing their normal things.”

When comparing the current hostilities with the 2006 war between Israel and Hezbollah, Abiad said: “Definitely we’re looking at a more cruel war, especially in the way civilians are being targeted.”

The UN Human Rights Office also expressed alarm at the number of casualties in Monday’s strikes, saying they could have violated international humanitarian law.

When asked by journalists about the audio and text messages sent by the Israeli military to people in Lebanon, telling them to evacuate areas near buildings where Hezbollah stored weapons, spokeswoman Ravina Shamdasani said: “Telling civilians to flee doesn’t make it ok to then strike those areas, knowing full well that the impact on civilians will be huge.”

Roads in southern Lebanon were also congested for a second day, as thousands more people fled north to get away from the Israeli attacks. Journeys that would usually take an hour were lasting 12 or more.

At a shelter in Beirut, 65-year-old Maryam told the BBC that she had travelled all night with 12 relatives in one small car.

“We got together and left. We didn’t want to leave our homes, because leaving your home is difficult,” she said. “We arrived here at four in the morning. With our children. It’s because of our children that we left.”

During a visit to an intelligence base, Prime Minister Benjamin Netanyahu said Israel would “continue striking Hezbollah” until it had achieved its war goal of returning displaced Israeli civilians to their homes along the northern border.

He also addressed the people of Lebanon, insisting that “our war is not with you” and warning them that Hezbollah leader Hassan Nasrallah was “leading you to the edge of the abyss”.

“I told you yesterday to evacuate homes in which there is a missile in the living room and a rocket in the garage. Whoever has a missile in the living room and a rocket in the garage will no longer have a home,” he said.

Israeli military spokesman Rear Admiral Daniel Hagari told an evening briefing that Hezbollah had turned southern Lebanon and the Bekaa Valley “into a combat zone” and that aircraft had continued to strike targets there throughout Tuesday.

He also released video footage that he said showed secondary explosions during strikes on residential buildings that indicated missiles and a truck carrying a rocket launcher had been stored inside them.

Hagari also said the head of Hezbollah’s missile and rocket unit, Ibrahim Qubaisi, had been killed in an air strike in Beirut’s southern suburbs on Tuesday afternoon, along with at least two other commanders who were with him at the time.

Qubaisi was “a key figure in activating missiles” and was “responsible for a series of attacks on Israeli territory”, he added.

The Lebanese health ministry said six people were killed and 15 others injured in an “Israeli enemy raid” that partly destroyed the top two floors of a block of flats in Beirut’s Ghobeiry neighbourhood.

There was no immediate comment from Hezbollah, but a source close to the group confirmed to AFP news agency that Qubaisi had been killed.

Hezbollah did, however, say that its fighters had fired barrages of rockets towards more than a dozen Israeli towns and military bases, as well as an explosives factory. It also claimed that a new type of rocket had been used to strike the IDF’s Samson unit.

Sirens continued to sound throughout the day across northern Israel and interceptor rockets from Israel’s Iron Dome air defence system were seen streaking into the sky.

Some of the approximately 300 rockets landed, causing damage and injuring six civilians and soldiers, most of them lightly, according to Hagari.