© USGS
The head of Venezuela's emergency services, Luis Diaz Curbelo told Reuters the quake, which hit at about 3:40 p.m. local time/2010 GMT, was felt across the country.
The U.S. Geological Survey said the quake occurred 23 miles north-northeast of Puerto Cabello, one of the OPEC nation's main oil ports. The epicenter was below the sea at a depth of 6.2 miles.
Television reported smaller aftershocks in some regions.
One of Venezuela's main oil refineries, El Palito, and a petrochemicals complex are located in the region where the tremor was felt most strongly.
The quake also hit the country's oil heartland of Zulia, where buildings wobbled in state capital Maracaibo. But there were no initial reports of damage to oil installations.
Oil company PDVSA was not immediately available for comment.
Cellular telephone networks jammed with the quantity of calls after the tremor. A Reuters witness said power was out in one part of Caracas and media reports said other regions were also without electricity.
Hipolito Izquierdo, who heads the national electricity company, denied problems with the service.
"The electricity service is normal everywhere in the nation," he said on state television.
In the capital Caracas, people streamed out of their apartment buildings and gathered on the streets despite heavy rain that flooded parts of the city with waist-deep water and knocked over trees.
"The security forces are working to gather reports of damage, in actions to recover any services, electricity, telephones, gas or water that may have failed because of the earthquake," said Jesse Chacon, minister of light industry and a close aide to President Hugo Chavez.
Quakes registering magnitude 6.0 or higher are considered capable of severe damage.
Earlier the USGS reported said the temblor was a 7.0 magnitude quake.
Comment: With the military build-up encircling Venezuela, it's worth noting that the US military has long studied and pioneered the Earth as a Weapon in 21st Century Wars.