Britain's Queen Elizabeth II said in a message of condolence to the president of the Lebanon on Wednesday that she was "deeply saddened" by the huge blast in capital Beirut that killed at least 100 people.
"Prince Philip and I were deeply saddened by news. Our thoughts and prayers are with the families and friends of those who have been injured or lost their lives, and all those whose homes and livelihoods have been affected," said the message released by Buckingham Palace.
Two huge explosions rocked the Lebanese capital Beirut on Tuesday, wounding dozens of people, shaking buildings and sending huge plumes of smoke billowing into the sky.
Lebanese media carried images of people trapped under rubble, some bloodied, after the massive explosions, the cause of which was not immediately known.
A security source confirmed that two explosions shook the port area of the city, Lebanon's largest urban area, leaving dozens wounded.
An AFP correspondent at the scene said every shop in the Hamra commercial district had sustained damage, with entire shopfronts destroyed, windows shattered and many cars wrecked.
Injured people were walking in the street, while outside the Clemenceau Medical Centre, dozens of wounded people, many covered in blood, were rushing to be admitted to the centre including children.
Destroyed cars had been abandoned in the street with their airbags inflated.
A huge cloud of black smoke was engulfing the entire port area, the AFP correspondent said.
The loud blasts in Beirut's port area were felt across the city and beyond and some districts lost electricity.
"Buildings are shaking," tweeted one resident, while another wrote: "An enormous, deafening explosion just engulfed Beirut. Heard it from miles away."
Online footage from a Lebanese newspaper office showed blown out windows, scattered furniture and demolished interior panelling.
The explosions came at a time when Lebanon is suffering its worst economic crisis in decades, which has left nearly half of the population in poverty.
Lebanon's economy has collapsed in recent months, with the local currency plummeting against the dollar, businesses closing en masse and poverty soaring at the same alarming rate as unemployment.
The explosions also come as Lebanon awaits the verdict on Friday on the 2005 murder of former Lebanese premier Rafic Hariri, killed in a huge truck bomb attack.