The death toll from a huge explosion that rocked Beirut on Tuesday has reached 100, the Lebanese Red Cross has said, and more victims are under the rubble.

The organisation told Lebanese TV the Red Cross was coordinating with the health ministry for morgues to take victims because hospitals were overwhelmed.

On Wednesday morning, smoke was still rising from the port where a towering grain silo was shattered.  Major streets in the city were littered with debris and damaged vehicles, and building facades were blown out.

It remains unclear what caused the largest blast, which appeared to have been triggered by a fire near a storage facility housing volatile chemicals.

The explosion struck with the force of a 3.5 magnitude earthquake, according to Germany's geosciences centre GFZ, and was heard and felt as far away as Cyprus, more than 180 miles across the Mediterranean.

It sparked further fires, overturned cars and blew out thousands of windows and doors.

It was the most powerful explosion ever seen in the city, which was on the front lines of the 1975-1990 civil war and has endured conflicts with neighbouring Israel and periodic bombings and terror attacks.

The devastating explosions came as the city’s hospitals were already confronting a surge in coronavirus cases, and there are now major concerns the virus could spread further as thousands of injured people flood into hospitals.

Lebanese soldiers search for survivors after a massive explosion in Beirut, Lebanon, Wednesday, Aug. 5, 2020. The explosion flattened much of a port and damaged buildings across Beirut, sending a giant mushroom cloud into the sky. In addition to those who died, more than 3,000 other people were injured, with bodies buried in the rubble, officials said.(AP Photo/Hassan Ammar)© ASSOCIATED PRESS Lebanese soldiers search for survivors after a massive explosion in Beirut, Lebanon, Wednesday, Aug. 5, 2020. The explosion flattened much of a port and damaged buildings across Beirut, sending a giant mushroom cloud into the sky. In addition to those who died, more than 3,000 other people were injured, with bodies buried in the rubble, officials said.(AP Photo/Hassan Ammar)

Interior Minister Mohammed Fahmi told a local TV station it appeared the blast was caused by the detonation of more than 2,700 tons of ammonium nitrate that had been stored in a warehouse at the dock since being confiscated from a cargo ship in 2014.

Witnesses reported seeing an orange cloud which appears when toxic nitrogen dioxide gas is released after an explosion involving nitrates.

Videos showed what looked like a fire erupting nearby moments earlier, and local TV stations reported a fireworks warehouse was involved. The fire appeared to spread to a nearby building, triggering the explosion, sending up a mushroom cloud and generating a shock wave.