Two devastating earthquakes ripped through Venezuela on Wednesday evening, flattening buildings in Caracas and sparking fears that the disaster could leave tens of thousands dead.

The back-to-back tremors - measured at magnitudes 7.1 and 7.5 by the US Geological Survey (USGS) - struck near the coast, sending terrified residents racing out from swaying apartment blocks as walls collapsed and clouds of dust rose over the capital.

'High casualties and extensive damage are probable and the disaster is likely widespread,' the USGS said, 'with an initial death toll estimate likely between 10,000 and 100,000.'

No official number of people killed or injured had been released by Venezuelan authorities by Thursday morning, but terrifying footage showed the scale of the destruction unfolding across the Venezuela capital.

Emergency workers were seen clambering into the ruins of a collapsed building as night fell, while distraught residents stood outside shattered homes and apartment blocks with entire walls torn away, leaving furniture exposed to the street.

Interior Minister Diosdado Cabello confirmed that buildings and homes had been brought down in the capital.

'Some buildings have been brought down (in Caracas), houses have collapsed,' he said on state television.

One witness described cracks racing up the side of their apartment block as the ground buckled, while others fled into the streets and refused to return inside.

In the coastal state of Falcon, Governor Víctor Clark said 32 people had been hospitalized and more than four hours after the earthquake there were still 15 people trapped.

President Donald Trump said the United States was preparing to help Venezuela after the devastation.

'The U.S.A. stands ready, willing, and able to help! I have instructed all agencies of our government to get ready to move quickly,' Trump wrote shortly before midnight. 'We will be there for our new and great friends. Early reports are not good!!!'

The quakes struck while many Venezuelans were at home marking Battle of Carabobo Day, the public holiday commemorating the 1821 victory that helped secure the country's independence from Spain.