AN enormous explosion has hit Lebanon's capital of Beirut.

Lebanese Red Cross official Georges Kettaneh said there were dead and wounded, but did not have an exact figure – just saying there were hundreds of casualties.

A civil defence official on the scene of the blast said his men had evacuated dozens to hospitals and that there were still bodies inside the port, many of them under debris.

The afternoon blast shook several parts of the capital and thick smoke billowed from the city centre.

The cause of the blast was not immediately known, but 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.

Local television channel LBC said the material was sodium nitrate.

Local campaigner Bissan Fakih posted this video.

The country's health minister said it was caused by an explosion on a ship carrying fireworks in the port, with reports of a fire and several smaller explosions at the port before the main blast. 

The head of the Lebanese Red Cross told local TV there were hundreds of casualties although many were superficial wounds from broken glass.

Videos taken by residents showed a fire raging at the port, sending up a giant column of smoke, illuminated by flashes of what appear to be fireworks. Local TV stations reported that a fireworks warehouse was involved.

The fire then appeared to catch at a nearby building, triggering a more massive explosion, sending up a mushroom cloud and a shock wave over the city.

Journalist Joe Truzman tweeted these images.

Miles from the port, balconies were knocked down, windows shattered, streets were covered with glass and bricks and lined with wrecked cars. Motorcyclists picked their way through traffic, carrying the injured.

BBC reporter Quentin Sommerville posted this video of the carnage in the aftermath.

A local journalist showed the devastation in the nearby office of The Daily Star Lebanon, around 400 metres from the blast site.

The explosion comes as the country faces its worst economic and financial crisis in decades.

There are also rising tensions between Israel and the militant Hezbollah group along Lebanon's southern border.

Local Fady Roumieh was stood in the car park to shopping centre ABC Mall Achrafieh, around 2km east of the blast, when the explosion occurred.

"[It was] like a nuclear bomb," he told the PA news agency. "The damage is so widespread and severe all over the city. Some buildings as far as 2km are partially collapsed.

"It's like a war zone. The damage is extreme. Not one glass window intact."

Roumieh said the incident has been compounded by the current political climate in the city amid the coronavirus pandemic.

"And the emotional trauma to this city is what's worst," he added.

"On top of the pandemic. The total economic meltdown. And currency devaluation."