A magnitude 7.2 earthquake struck about 160 km west of the capital Caracas on Wednesday evening, followed less than a minute later by a magnitude 7.5 tremor, the strongest since 1900, according to the US Geological Survey.
The US, which in January staged an operation to seize then Venezuelan president Nicolas Maduro, moved to ease sanctions to allow aid into the country.
The disaster hit a country already weakened by years of economic turmoil, which left much of its infrastructure fragile and complicated rescue efforts as aftershocks rattled the capital and surrounding coastal areas.
The confirmed death toll from the two back-to-back earthquakes has risen to around 235, Health Minister Carlos Alvarado said in an interview with state television on Thursday.
"We've unfortunately received about 235 patients who arrive without vital signs or who pass away as they're arriving at our health centres," Alvarado said.
Earlier, Jorge Rodriguez, head of Venezuela's national assembly and brother of interim President Delcy Rodriguez, said some 200 people were trapped and 1,520 had been hospitalised. He said 250 buildings were damaged or destroyed.
At least eight hospitals, the headquarters of the Venezuelan Red Cross and the French embassy were among buildings reported to have been badly damaged.
Interior Minister Diosdado Cabello said 70,000 families in La Guaira state, home to the capital's main airport, had been affected.
"It has become a disaster zone," acting President Rodriguez said, adding that the government was working with private companies to bring in heavy equipment and speed up rescues.
Emergency workers and volunteers searched through collapsed buildings into the night, but resources were stretched.
Yamileth Jimenez, a resident of La Guaira city, said her 19-year-old son was still trapped in the debris of their seven-storey apartment building.
"He's under the slabs and there's no machinery to get him out," said Jimenez.
In La Guaira city, volunteers dug through wreckage with their bare hands as families waited for news of missing relatives. Along the Caracas-La Guaira highway, streams of civilians headed toward the coast carrying water, food and medicine, stepping in as the scale of the disaster overwhelmed initial rescue efforts.
Many Venezuelans were at home when the quakes struck during a public holiday. Residents rushed out of shaking buildings and into the streets as structures swayed or collapsed across Caracas and nearby coastal communities.
Near the epicentre in Moron, a seaside town in Carabobo state, houses crumpled and residents were left without water or electricity.
The US Geological Survey's predictive modelling indicated the death toll was likely to rise into the thousands, with a substantial probability of exceeding 10,000.
A website created to track missing people listed more than 46,000 people as unaccounted for.
Countries around the world pledged support, even some that have opposed Venezuela, which has suffered decades of international isolation amid a spiral of political repression, economic collapse and diplomatic pressure.
Rodriguez said international rescue teams were expected soon and thanked leaders including US President Donald Trump and Russian President Vladimir Putin.
Trump said the United States was "ready, willing and able to help." US Secretary of State Marco Rubio said Washington would send rescue teams while the Pentagon would help with logistics and support Caracas' damaged airport.
UN aid chief Tom Fletcher said the organisation was coordinating international rescue teams and "a massive collective effort" would be needed in a country where 8 million people required humanitarian assistance before the quake.
SpaceX's Starlink said it would provide free service in affected areas and was working to deploy terminals to the hardest-hit zones to help restore communications.
In the country's economically vital oil sector, foreign energy companies said their operations had not suffered major disruption and oil infrastructure appeared largely spared.
with DPA
