Lebanon's Interior Minister Mohammed Fehmi said the huge explosions may have been caused by explosive materials that were stored at Beirut port.

General Security Chief Abbas Ibrahim said: "It appears that there is a warehouse containing material that was confiscated years ago, and it appears that it was highly explosive material".

Speaking to reporters, he said a probe would begin, but added "we cannot preempt investigations".

Image source, EPA

The head of the Lebanese Red Cross told local media that hundreds of people have been injured in the explosion.

Georges Kettaneh said he could not put a more exact figure on the number of people wounded because many were still trapped in the area of the blast.

He told Lebanon's LBC television that the Red Cross had been "overwhelmed" with calls since the explosion.

The group said all of its available ambulances had been dispatched to help with rescue efforts.

Hospitals are also said to be overwhelmed with casualties.

AFP correspondent Maya Gebeily said some were turning away injured people because they were too full.

Local media quoted the Hotel Dieu Hospital in Beirut as saying that it was treating more than 500 injured patients and was not able to receive any more.

The hospital is appealing for blood donations.

Marianna Spring
Specialist disinformation and social media reporter

Unfounded claims suggesting what’s happened in Beirut is a nuclear explosion, a US bomb or an attack by Israel on Lebanon are circulating on social media.

Such claims have been shared by a number of partisan news sites amidst speculation online over the cause of the blaze.

Major General Abbas Ibrahim, director of General Security, has told Lebanese media that the most likely source of the blast was a depot at the port, where highly explosive materials had been stored.

He also dismissed allegations that Israel was to blame. An Israeli minister has also refuted suggestions the country had something to do with the incident.

Footage of a huge explosion followed by a mushroom cloud in Beirut is being shared around the world.

The blast - that has caused widespread damage and injured many people in the Lebanese capital - was reportedly felt hundreds of kilometres away.

Sebastian Usher
BBC Arab Affairs Editor

The videos and images not just of the massive cloud of smoke erupting in Beirut but the damage and devastation it's caused kilometres away have triggered a new wave of shock and anxiety in Lebanon, which is already teetering on the brink of a catastrophic economic collapse.

Just hours before the blast, anti-government protesters had been scuffling with the security forces outside the ministry of energy, demanding yet again accountability from the country's leaders.

There have been grave warnings of hunger in the streets or a reigniting of sectarian conflict if the economy worsens.

And the blast will remind many of the bomb that killed former Prime Minister Rafik Hariri in 2005. The Lebanese will be hoping that this latest blast will remain a human tragedy - an accident - and not a premeditated act.

Image source, EPA

Here's a quick recap of what we know so far about the explosion in Beirut.

• A large blast hit the Lebanese capital, causing widespread damage
• Prime Minister Hassan Diab declares Wednesday a "national day of mourning" after the country's health minister said there had been a "very high number of injuries"
• Reuters news agency reports that there had been at least 10 deaths, but there are no official figures yet
• Video posted online shows a large mushroom cloud and destroyed buildings in the city's port area
• The cause of the blast remains unknown, but several officials have been quoted as saying that explosives were being stored in warehouses at the port
• Emergency services are at the scene, with local media footage showing people trapped beneath the rubble

Image source, Getty Images

Lebanon's Prime Minister Hassan Diab has announced that tomorrow will be a "national day of mourning".

As yet there are no official word on casualties, but officials have said there could be a "very high number of injuries".

President Michael Aoun has called the Supreme Defence Council for an "urgent" emergency meeting this evening in Baabda Palace.

The cause of the blast remains unknown.

People in Cyprus - an island around 240 km (150 miles) from Beirut - have reported feeling the blast.

One resident of the capital Nicosia said his house shook, according to the Reuters news agency.

Journalist Emilia Papadopoulos said she felt the explosion in Limassol and thought it was an earthquake.

Image source, EPA

As yet there's been no official cause given for the massive explosion in Beirut.

Major General Abbas Ibrahim, director of General Security, has told Lebanese media that the most likely source of the blast was a depot at the port, where highly explosive materials had been stored.

Two security sources also told Reuters news agency there were warehouses there housing explosives.

The director general of customs has been quoted as saying that nitrate was the cause of the huge explosion.

Maj Gen Ibrahim reportedly dismissed allegations that Israel was to blame, and an Israeli minister told Reuters news agency that the country had nothing to do with the incident.

Israel's Foreign Minister Gabi Ashkenazi told a local television station that the explosion was most likely an accident caused by a fire.

Internet monitoring service NetBlocks says there has been a significant internet outage in Lebanon following the explosion.

It said analysis is ongoing to determine the cause of the outage, noting that it is unclear if or how it is related to the blast.

"The outage may impact ability to communicate with eyewitnesses on location," it said.

At least 10 bodies have been taken to hospitals following the blast, a Lebanese security source and a medical source told the Reuters news agency.

It's not yet clear what caused the explosion. Some local reports suggest it could have been accident at a firework storage warehouse.

Footage from Beirut shows extensive damage after a huge explosion.

The cause of the blast is not yet known.

Marianna Spring
Specialist disinformation and social media reporter

During a major breaking news event like this one, old photos, misleading claims and conspiracy theories are often shared on social media.

There are currently a number of what appear to be authentic videos of what’s happened in Beirut being shared on Twitter and WhatsApp. Most show the explosion in the Lebanese capital from different angles.

There are also videos of the aftermath of the explosion, some of which could show distressing scenes.

It's a reminder that breaking news events are a fertile time for misinformation and speculation online.

Before you share a post on social media:

1. Interrogate the source. Have the claims been reported in reliable places? Are the images or video old or manipulated?
2. Think about bias. Has the post been shared with an ulterior motive? And does it confirm a pre-existing bias or feed into a polarised conversation online?
3. Is it helpful? Even if the claims were true, would it be useful to share them? And would it be respectful to those affected?

Image source, EPA

Beirut's port zone has been cordoned off, with only emergency services and relatives of those who had been working in the area given access, AFP news agency reports.

A string of ambulances and fire trucks were rushing to the port area, with their sirens sounding.

The Ministry of Health tweeted that hospitals had been instructed to take in those wounded by the explosion at the government's expense.

The scale of casualties is not known, but as we mentioned earlier Health Minister Hamad Hasan has been quoted as saying there are a "very high number of injuries".

Photos are emerging from the scene of the blast.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, Reuters

Eyewitness Hadi Nasrallah has spoken to the BBC about the moment of the explosion.

He said the blast - the cause of which is currently unknown - was "very scary" and "very, very loud".

You can watch the full interview here:

Image source, Reuters

Witnesses in Beirut have described the moment of the explosion and its aftermath.

One told the BBC that the blast was so big he thought he was going to die. He said windows were shattered and buildings damaged.

Another told Reuters news agency people were "screaming and running, bleeding."

"Balconies were blown off buildings. Glass in high-rise buildings shattered and fell to the street," the witness said.

A woman described seeing heavy smoke in Beirut's port area before hearing the explosion.

"All the downtown area windows are smashed and there are wounded people walking around. It is total chaos."

Image source, Reuters

Lebanon's Health Minister Hamad Hasan says the explosion has caused a "very high number of injuries", local broadcaster LBC reported.

The minister also said it had caused a large amount of damage.

Al Mayadeen television said hundreds were wounded.

It was not immediately clear what caused the blast.

Good evening from the BBC World online team in London. A massive explosion has rocked the Lebanese capital Beirut. We’ll be bringing you all the latest updates here.

This is what we know so far:

• Reports say the explosion was in the port area of the city and video footage from the scene showed a large mushroom cloud and extensive damage
• Dozens of people have been injured, according to AFP news agency
• The blast came ahead of a verdict in a trial for the 2005 killing of ex-PM Rafik Hariri
• There are unconfirmed reports of a second blast at the Hariri residence in the city

Read the full news story here