Strong earthquakes struck west of Venezuela's capital on Wednesday afternoon, bringing down buildings in Caracas and causing scientists to estimate "high casualties and extensive damage" to the South American country.

A magnitude 7.2 earthquake struck about 160 km (100 miles) west of Caracas, with a magnitude 7.5 tremor hitting less than a minute later, according to the U.S. Geological Survey (USGS).

"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.

Authorities did not immediately give estimates for deaths or injuries. "Some buildings have been brought down (in Caracas), houses have collapsed," Interior Minister Diosdado Cabello said on state television.

Video footage showed emergency workers climbing into the ruins of one collapsed building in the capital as night began to fall.

Many Venezuelans were at home when the quakes hit, celebrating a public holiday commemorating an 1821 military victory which secured Venezuela's independence from Spain.

"As soon as it started, we began hearing people screaming," said Astrid Ramirez, a 41-year-old publicist in western Caracas. "Everyone was running down the stairs."

Venezuela sits on a seismically active tectonic region where the Caribbean Plate collides with the South American Plate.

Residents in the capital, which was also rocked by a deadly magnitude 6.3 earthquake in 1967, rushed to evacuate as the quake shook buildings.

"There was a very loud crash. Things fell in the house, jugs inside the refrigerator. I've never experienced anything like it," said Coro Martinez, 56, who lives in eastern Caracas.

Maria Romero, an 80-year-old pensioner on the south side of Caracas, said that the police helped her get out. "This earthquake was horrible, even worse than the one in 1967," she added.

Fire trucks could be seen on the streets in the capital, and the facades of some buildings had suffered significant damage.

The U.S. Tsunami Warning System issued a tsunami threat for Puerto Rico and the U.S. and British Virgin Islands following the earthquake, adding that islands off the coast of Venezuela — Aruba, Curacao and Bonaire — could also be hit by hazardous waves. It withdrew the warning within about an hour.