Beirut explosion: What we know so far
The disaster was preceded by a large fire at the Port of Beirut, on the city's northern Mediterranean coast.
In videos posted on social media white smoke could be seen billowing from Warehouse 12, next to the port's huge grain silos.
Shortly after 18:00 (15:00 GMT), the roof of the warehouse caught alight and there was a large initial explosion, followed by a series of smaller blasts that some witnesses said sounded like fireworks going off.
About 30 seconds later, there was a colossal explosion that sent a mushroom cloud into the air and a supersonic blastwave radiating through the city.