Venezuela's interim leader declared a state of emergency Wednesday as two massive earthquakes caused buildings in the capital to crumble and forced the closure of the country's main airport, prompting US President Donald Trump to offer aid.

Delcy Rodriguez said 20 aftershocks had followed the earthquakes of magnitude 7.2 and 7.5, which struck the same area of Venezuela, according to the United States Geological Survey (USGS).

The quakes triggered panic in the capital and drove people into the streets, AFP journalists saw.

"The stairs came away, the whole wall cracked. Things fell from the ceiling. It was horrible," said 54-year-old bank employee Odalis Escalona.

It remained unknown if there were fatalities, but some people were injured and buildings had collapsed, Interior Minister Diosdado Cabello said.