Video report by ITV News correspondent John Ray
At least 70 people are dead after a massive explosion in Lebanon's capital Beirut on Tuesday afternoon, an official has confirmed.
Lebanese health minister, Hassan Hamad also said more than 3,000 were injured in the blast.
A huge mushroom cloud was seen over the capital and thick smoke billowed over the city centre. Residents reported feeling the blast from miles away from the epicentre.
Videos posted on social media showed a fire raging at the port and a large plume of smoke stretching hundreds of metres into the sky.
The fire then appeared to catch at a nearby building, triggering a more massive explosion, sending up a mushroom cloud and a shock wave.
According to reports, it could be heard and felt as far away as Cyprus, more than 180 miles across the Mediterranean and struck with the force of a 3.5 magnitude earthquake, according to Germany’s geosciences centre GFZ.
Lebanese Prime Minister Hassan Diab said that Wednesday would be a day of mourning and indicated that the blast came from a "dangerous" warehouse.
"I promise you that this catastrophe will not pass without accountability," he said "Those responsible will pay the price."
He added: "Facts about this dangerous warehouse that has been there since 2014 will be announced and I will not preempt the investigations".
What we know so far:
The explosion came from the port area of Beirut, causing destruction for miles around.
Footage shows an initial fire, which is believed to have spread to a neighbouring building, causing a large explosion that sent a mushroom cloud over the city.
There are more than 3,000 casualties, many suffering from superficial wounds caused by broken glass. At least 70 have been confirmed dead.
Abbas Ibrahim, chief of Lebanese General Security, said it might have been caused by highly explosive material that was confiscated from a ship some time ago and stored at the port.
Lebanese PM Hassan Diab indicated the blast came from a "dangerous warehouse" and warned those responsible will "pay the price".
Government sources have suggested that it was possibly caused by ammonium nitrate stored at the docks.
Prime Minister Boris Johnson confirms British nationals are among those caught up in the aftermath of the blast.
The cause of the blast, which sparked fires, overturned cars and blew out windows and doors, was not immediately known.
Local media had reported it took place in the city port inside an area where firecrackers were stored.
But the chief of Lebanese General Security Abbas Ibrahim dismissed the claims, saying that it was a "high-explosive material" confiscated from a ship some time ago that was stored there.
Government sources have suggested that the cause was highly explosive materials, possibly ammonium nitrate stored at the docks.
Witnesses reported seeing an orange-coloured cloud over the site after the explosion.
Orange clouds of toxic nitrogen dioxide gas often accompany an explosion involving nitrates.
An Associated Press photographer near Beirut’s port witnessed people wounded on the ground and widespread destruction flattening much of the port.
A civil defence official on the scene said dozens had been evacuated to hospitals and that there were still bodies inside the port, many of them under debris.
Dozens of ambulances ferried the injured from the port area, where the wounded lay on the ground, Associated Press staff at the scene said.
The devastation overwhelmed a country already struggling with an economic crisis and the coronavirus pandemic.
Several of the city's hospitals were damaged in the blast with several calling for blood and spare generators to keep its electricity going.
Outside the St. George University Hospital in the Achrafieh neighborhood, dozens were treated in the streets as damage to the building knocked out its electricity.
“This is a catastrophe we have on our hands,” said one doctor, speaking on condition of anonymity.
Witnesses reported windows and doors blowing out and false ceilings dropping with many people injured by flying glass and debris.
Beirut’s governor, Marwan Abboud and broke into tears as he toured the site.
“Beirut is a devastated city,” he said.
Hadi Nasrallah, who was travelling in a taxi some distance from the epicentre of the blast, said: "You can hear it was loud, the house moved.
"It felt as if it went inside us, it passed through our soul in a wave.
"I saw something bright and I lost my hearing for a few seconds."
“It was like a nuclear explosion,” said Walid Abdo, a 43-year-old school teacher in the neighbourhood of Gemayzeh.
Prime Minister Boris Johnson has confirmed that British nationals are among those caught up in the aftermath of the blast.
He said the government is “ready to provide support in any way we can”.
In a tweet, he said: "The pictures and videos from Beirut tonight are shocking. All of my thoughts and prayers are with those caught up in this terrible incident.
"The UK is ready to provide support in any way we can, including to those British nationals affected."
Foreign Secretary Dominic Raab said: “The UK stands in solidarity with the people of Lebanon and is ready to offer help and support, including to those British nationals impacted.”
Lebanon's state-run NNA news agency said a major fire broke out near the port and firefighters were at the scene.
Charbel Haj, who works at the port, said it started as small explosions like firecrackers, then the huge blast erupted and he was thrown off his feet and his clothes were torn.
Beirut journalist Patricia Bou Nassif said it felt like an "earthquake" at first.
"Then we felt a big explosion and my boy was screaming," she said. "I knew this was an explosion because it was the same sound I heard in 2005 when they assassinated Prime Minister [Rafik] Hariri."
"It was like a war, a nuclear explosion," she said.
She added: "It is something very dangerous. Even in the street I could not breathe because of the smoke."
Miles from the port, balconies were knocked down, windows shattered, streets were covered with glass and bricks and lined with wrecked cars.
Shock waves from the blast blew through windows and caused widespread damage to homes and businesses.
Video taken in a nearby shopping mall shortly after the blast showed the devastation.
Save the Children, which has offices in Beirut three miles from the harbour, said members of their team have reported entire streets destroyed and children unaccounted for.
Despite the charity’s offices in the city being badly damaged, they have pledged that a rapid response team is ready to offer support.
Jad Sakr, Save the Children’s country director in Lebanon, said: “We are shocked and devastated by the explosion today.
“The death toll may not be known for several days but we do know is that in a disaster like this, children may be hurt, shocked and separated from their parents.
“Our child protection teams are ready to support the government’s efforts, which will almost certainly go on for several days to come."
He added: “The incident could not have occurred at a worst time and has hit communities who were already suffering from the impact of the Covid-19 crisis and the economic deterioration.
“Beirut’s main port, now completely damaged, is vital for much of the food, grains and fuel that Lebanon imports, and families will immediately feel the shortage in basic needs as a result of this tragedy.”
The blast took place only three days before a UN-backed tribunal was set to give its verdict in the killing of former Prime Minister Rafik Hariri in a truck bombing more than 15 years ago.
It also comes amid rising tensions between Israel and the militant Hezbollah group along Lebanon’s southern border.
ITV News Senior International Correspondent John Irvine, currently in Tel Aviv, says it is not in Israel’s interests to destabilise Lebanon any further, given their already-dire economic situation.
Earlier on Tuesday, Prime Minister Benjamin Netanyahu warned Hezbollah that Israel would not hesitate to strike again if it felt it was necessary.
An Israeli government official later said his country “had nothing to do” with the blast.