Nine people, including a child, have been killed after handheld pagers used by members of the armed group Hezbollah to communicate exploded across Lebanon, the country’s health minister says.

Iran’s ambassador to Lebanon was among 2,800 other people who were wounded by the simultaneous blasts in Beirut and several other regions.

Hezbollah, which is backed by Iran, said the pagers belonged “to employees of various Hezbollah units and institutions” and confirmed the deaths of eight fighters.

The group blamed Israel for what it called “this criminal aggression” and vowed that it would get “just retribution”. The Israeli military declined to comment.

Hours before the explosions, Israel’s security cabinet said stopping Hezbollah attacks on the north of the country to allow the safe return of displaced residents was an official war goal.

There have been almost daily exchanges of fire across the Israel-Lebanon border since the day after the start of the war between Israel and Hamas in Gaza on 7 October.

Hezbollah has said it is acting in support of the Iran-backed Palestinian group.

In its latest statement on Wednesday, Hezbollah said it would carry on its "operations in support of Gaza", adding that this was a “continuous path separate from the hard price that awaits the enemy in response to its massacre on Tuesday”.

Both Hezbollah and Hamas are proscribed as terrorist organisations by Israel, the UK and other countries.

The UN's spokesman said the latest developments in Lebanon were "extremely concerning, especially given that this is taking place within a context that is extremely volatile".

Many Lebanese were in a state of shock and disbelief on Tuesday evening, unable to get their heads around an event that was unprecedented in scale and nature.

Hezbollah said an unspecified number of pagers - which the group relies on heavily for communications due to the risk of mobile phones being hacked or tracked - exploded at around 15:30 local time (12:30 GMT) in the capital Beirut and many other areas.

One CCTV video showed an explosion in a man’s bag or pocket at a supermarket. He is then seen falling backwards to the ground and crying out in pain as other shoppers run for cover.

Hours later, ambulances were still rushing to hospitals overwhelmed with the number of casualties, 200 of whom the health minister said were in a critical condition. Outside, relatives were waiting in the hope of receiving updates.

The LAU Medical Centre in Beirut's Ashrafieh district closed its main gate and was limiting the number of people getting in. “It’s very sensitive and some scenes are horrific,” one staff member told the BBC.

Most of the wounds were at the level of the waist, face, eyes and hands, he said, adding: “A lot of casualties have lost fingers, in some cases all of them.”

The wife of Iranian ambassador Mojtaba Amani said he was "slightly injured" by one of the explosions and that he was "doing well" in hospital.

Hezbollah's media office announced the deaths of eight fighters. It did not give details on the locations and circumstances, saying only that they were “martyred on the road to Jerusalem".

A source close to the group told AFP news agency that the son of Hezbollah MP Ali Ammar and the 10-year-old daughter of a Hezbollah member in the Bekaa Valley were among those killed. Later, the source said the son of another lawmaker, Hassan Fadlallah, was wounded, having initially reported that he was dead.

Fourteen people were also wounded by exploding pagers in neighbouring Syria, where Hezbollah is fighting alongside government forces in the country's civil war, according to the UK-based Syrian Observatory for Human Rights.

“We hold the Israeli enemy fully responsible for this criminal aggression,” Hezbollah said in a statement on Tuesday evening.

“This treacherous and criminal enemy will certainly get his just retribution on this sinful aggression from where it counts and from where it does not count,” it added.

Lebanese Prime Minister Najib Mikati also blamed Israel for the explosions, saying that they represented a “serious violation of Lebanese sovereignty and a crime by all standards”.

Iranian Foreign Minister Abbas Araghchi said he told his Lebanese counterpart that he "strongly condemned Israeli terrorism".

The US, Israel's closest ally, denied any involvement and urged Iran not to heighten tensions.