Qatar expresses solidarity with Lebanon
*Explosion sends seismic shock across Lebanon
*Highly explosive materials stored at port: minister
* Blast felt in Cyprus, more than 180 km away
A huge explosion in a port warehouse district near the centre of Beirut killed more than 50 people, injured over 2,700 others and sent shockwaves across the Lebanese capital on Tuesday, shattering windows and causing apartment balconies to collapse.
Officials expected the death toll to rise sharply as emergency workers dug through rubble across a swathe of the city to rescue people and remove the dead. It was the most powerful blast to hit Beirut in years, making the ground tremble.
"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 - in all the streets and areas near and far from the explosion."
Three hours after the blast, which struck shortly after 6pm (1500 GMT), 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.
A security source said victims were being taken for treatment outside the city because Beirut hospitals were already packed with wounded. Red Cross ambulances from the north and south of the country and the Bekaa valley to the east were called in to cope with the huge casualty toll.
The blast was so big that some residents in the city, where memories of heavy shelling during the 1975 to 1990 civil war live on, thought an earthquake had struck. Dazed, weeping and, wounded, people walked through streets searching for relatives.
Lebanon's interior minister said initial information indicated highly explosive material, seized years ago, that had been stored at the port had blown up. The minister later told Al Jadeed TV ammonium nitrate had been in storage there since 2014.
Footage of the explosion shared by residents on social media showed a column of smoke rising from the port district followed by an enormous blast, sending a ball of white smoke and fireball into the sky. Those filming the incident from high buildings 2 km from the port were thrown backwards by the shock.
Lebanon's health minister said more than 30 people had been killed and more than 2,500 were injured. Lebanon's Red Cross said hundreds of people had been taken to hospitals.
Lebanese President Michel Aoun called for an emergency meeting of the country's Supreme Defence Council, according to the presidency's Twitter account. Prime Minister Hassan Diab called for a day of mourning today.
The explosion occurred three days before a UN-backed court is due to deliver a verdict in the trial of four suspects from the Shi'ite group Hezbollah over a 2005 bombing which killed former Prime Minister Rafik al-Hariri and 21 other people.
Hariri was killed in another huge blast on the waterfront, although on that occasion it was caused by a truck bomb.
It was not immediately clear what caused the blaze that set off the blast.
Internal Security Chief Abbas Ibrahim, touring the port area, said he would not pre-empt investigations. An Israeli official said Israel, which has fought several wars with Lebanon, had nothing to do with the blast.
The governor of Beirut port told Sky News that a team of firefighters at the scene had "disappeared" after the explosion.
"I saw a fireball and smoke billowing over Beirut. People were screaming and running, bleeding. Balconies were blown off buildings. Glass in high-rise buildings shattered and fell to the street," said a Reuters witness.
Residents said glass was broken in houses from Raouche, on the Mediterranean city's western tip, to Rabieh 10 km east. In Cyprus, a Mediterranean island 180 km across the sea from Beirut, residents heard the blast bangs. One resident in Nicosia said his house and window shutters shook.
"All the downtown area windows are smashed and there are wounded people walking around. It is total chaos," a Reuters witness said.