The U.S. Geological Survey said powerful back-to-back earthquakes struck Venezuela on Wednesday evening, with a magnitude 7.2 foreshock followed just 39 seconds later by a stronger magnitude 7.5 mainshock near Moron along the country's Caribbean coast.

The agency's preliminary impact assessment estimated the disaster could result in 10,000 to 100,000 fatalities as buildings collapsed in Caracas and residents fled into the streets.

The earthquakes damaged buildings in the capital and sent terrified residents rushing outside with family members and pets.

Strong earthquakes are relatively rare in Venezuela despite its location near the boundary of the South American and Caribbean tectonic plates.

"The building really shook from side to side. Unreal. The force was incredibly strong," Caracas resident Roberto Gamas said.

"We were walking and it was tossing us around. Everything in the apartment fell. Thank God we were able to get out," Gamas said.

Another resident, Hector Ricci, described the escalating shaking: "It started off gently and then gradually grew, and in the end, we all had to leave our houses, go outside, and gather together."

Interior Minister Diosdado Cabello said the quakes were felt across several states and reported "alarming situations" in Caracas' Altamira neighborhood, where homes and buildings collapsed.

He urged motorists to clear roads for emergency responders and warned residents to remain outdoors because of the risk of aftershocks.

"We understand that some people may be desperate, but we are acting according to protocols to activate aid and rescue efforts to help those who need it most," Cabello said.

"Be very careful with children and the elderly; call each other and check that no one has been harmed."

Initial tsunami advisories were issued for parts of the Caribbean, including the U.S. Virgin Islands and the Dominican Republic, while an alert for Puerto Rico was later lifted.

The USGS subsequently said there was no tsunami threat.