The government said 235 dead had been taken to medical centres but did not give a total casualty estimate from the magnitude 7.2 and 7.5 tremors that struck about 160km west of Caracas on Wednesday.
A website created to track missing people and shared by opposition leaders from the politically polarised nation listed 49,500 people as unaccounted for, while the US Geological Survey predicted more than 10,000 deaths.
Spain's foreign ministry confirmed that two of its nationals had died with another 80 unaccounted for.
With foreign rescue teams arriving, firefighters, soldiers and distraught citizens combed through shattered buildings, some using bare hands and torches in places where power was down.
"He's under the slabs and there's no machinery to get him out," said Yamileth Jimenez of her 19-year-old son stuck in debris of their seven-storey apartment building in La Guaira city on the coast outside Caracas.
Thousands are homeless in a nation already weakened by decades of economic and political turmoil that has impoverished the nation, triggered an exodus of millions, and eroded basic infrastructure and services.
Many live in flimsy hillside slums called "barrios".
"My building is uninhabitable and now I have nothing. It's just me and my son, and I have no family in the country," said Suhayl Sarquiz, 50, who lost her job a few months ago.
"It's a tragedy," said Beatriz Rodriguez, 60, whose nephew's legs were amputated after he was crushed in the quakes. Another nephew was killed.
The government confirmed 250 buildings damaged or destroyed.
At least eight hospitals, the Venezuelan Red Cross and the French embassy were among buildings reported badly damaged.
La Guaira, the coastal state adjoining Caracas and home to the nation's main airport, was among the hardest-hit areas.
Streams of volunteers headed down the Caracas-La Guaira highway with water, food and medicine.
Near the epicentre in Moron, a seaside town in Carabobo state, houses crumpled and residents had no water or electricity.
Families salvaged what they could, including mattresses, televisions and washing machines.
Reuters journalists saw members of a "colectivo" - government-allied motorcycle groups long accused of harassing opposition supporters - assisting rescue efforts.
Nations around the world pledged support, even some that have opposed Venezuela during decades of international isolation, political repression and economic deterioration under the ruling Socialist Party.
Venezuela's interim President Delcy Rodriguez, who took over when the US seized her ally and former leader Nicolas Maduro in January, thanked both US President Donald Trump and Russian President Vladimir Putin for their efforts.
Washington eased sanctions to allow earthquake aid that would otherwise be prohibited.
President Donald Trump said the US 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.
Rodriguez posted footage of Mexican soldiers and sniffer dogs arriving at the damaged airport at La Guaira which was open only to state and military flights.
UN aid chief Tom Fletcher said the organisation was co-ordinating international rescue teams and "a massive collective effort" would be needed in a country where eight million people required humanitarian assistance before the quake.
The UN's Venezuelan human rights mission urged the government to lift restrictions on some social media, calling connectivity a "matter of life and death".
SpaceX's Starlink said it would provide free service through July 25 in affected areas.
In the OPEC member's vital oil sector, foreign energy companies said their operations had not suffered major disruption and oil infrastructure appeared largely spared.
Until now, the deadliest quake in Venezuela's modern history had been in 1967, killing 240 people.
with DPA
