BEIRUT (REUTERS) - Lebanese rescue workers are digging through rubble looking for survivors of a powerful warehouse explosion that shook the capital Beirut on Tuesday (Aug 4), killing 100 people and injuring nearly 4,000 in a toll that officials expect to rise.

The blast at port warehouses storing highly explosive material was the most powerful in years in Beirut, a city already reeling from an economic crisis and a surge in coronavirus infections.

SMOKE AND FIREBALL

Images showed port buildings reduced to tangled masonry, devastating the main entry point to a country that relies on food imports to feed its population of more than six million.

It threatens a new humanitarian crisis in a nation that hosts hundreds of thousands of Syrian refugees and which is already grappling with economic meltdown under one of the world's biggest debt burdens.

Residents said glass was broken in neighbourhoods on Beirut's Mediterranean coast and inland suburbs several kilometres away. In Cyprus, a Mediterranean island 180km across the sea from Beirut, residents heard the blast. One resident in Nicosia said his house and window shutters shook.

The blast revived memories of a 1975-90 civil war and its aftermath, when Lebanese endured heavy shelling, car bombings and Israeli air raids. Some residents thought an earthquake had struck.

"The blast blew me off metres away. I was in a daze and was all covered in blood. It brought back the vision of another explosion I witnessed against the US embassy in 1983," said Ms Huda Baroudi, a Beirut designer.

Those filming the incident from high buildings 2km from the port were thrown backwards by the shock. Bleeding people were seen running and shouting for help through clouds of smoke and dust in streets littered with damaged buildings, flying debris, and wrecked cars and furniture.

LEBANESE LEADERS RESPOND

President Michel Aoun said that 2,750 tonnes of ammonium nitrate, used in fertilisers and bombs, had been stored for six years at the port without safety measures, and he said that was "unacceptable".

He called for an emergency Cabinet meeting on Wednesday. Officials did not say what caused the blaze that set off the blast. A security source and local media said it was started by welding work being carried out on a hole in the warehouse.

"What we are witnessing is a huge catastrophe," the head of Lebanon's Red Cross George Kettani told broadcaster Mayadeen. "There are victims and casualties everywhere."

Hours after the blast, which struck shortly after 6pm (11pm Singapore time), a fire still blazed in the port district, casting an orange glow across the night sky as helicopters hovered and ambulance sirens sounded across the capital.

Prime Minister Hassan Diab promised there would be accountability for the deadly blast at the "dangerous warehouse", adding "those responsible will pay the price".

The United States embassy in Beirut warned residents about reports of toxic gases released by the blast, urging people to stay indoors and wear masks if available.

"There are many people missing. People are asking the emergency department about their loved ones and it is difficult to search at night because there is no electricity," Health Minister Hamad Hasan told Reuters.

He said 78 people were killed and nearly 4,000 injured. Footage of the explosion shared by residents on social media showed a column of smoke rising from the port, followed by an enormous blast, sending a white cloud and a fireball into the sky.

The wife of the Dutch ambassador to Lebanon was seriously injured by the blast, the Dutch Foreign Ministry said on Wednesday.

A spokesman said she had been admitted to hospital.

He said the blast had caused extensive damage to the Dutch embassy, also wounding four other people connected to it.

INTERNATIONAL REACTION

The explosion occurred three days before a United Nations-backed court is due to deliver a verdict in the trial of four suspects from the Shi'ite Muslim group Hezbollah over a 2005 bombing which killed former Prime Minister Rafik al-Hariri and 21 others. Mr Hariri was killed by a huge truck bomb on the same waterfront, about 2km from the port.

Israeli officials said Israel, which has fought several wars with Lebanon, had nothing to do with Tuesday's blast, and said their country was ready to give humanitarian and medical assistance. Shi'ite Iran, the main backer of Hezbollah, also offered support, as did Teheran's regional rival Saudi Arabia, a leading Sunni power.

At a White House briefing, US President Donald Trump indicated that the explosion was a possible attack, but two US officials, speaking on condition of anonymity, said initial information contradicted Mr Trump's view.

"The United States stands ready to assist Lebanon," Mr Trump said at a White House briefing. "It looks like a terrible attack."

When asked later about his depiction of the explosion, Mr Trump said that he had met some US generals who feel the blast was not "some kind of a manufacturing explosion type of event".

He told reporters that according to these unnamed generals "they seem to think it was an attack. It was a bomb of some kind".