Journalist Nicole Kolster was at home in Venezuela's capital city Caracas when her apartment started shaking violently.

"I saw the windows moving, and the only thing I could think to do was to get between the front door and a stone wall... to try to protect myself," she recounts.

Two earthquakes hit the city seconds apart on Wednesday, the first at a magnitude of 7.2 and the second at 7.5. Photos show collapsed buildings and people gathered on the streets, but the number of casualties and full extent of the damage is still unknown.

"It's the strongest quake I've ever felt in my life," Kolster tells BBC Mundo. "It was so strong that I thought the building was going to fall on top of me."

Kolster stayed wedged between the front door and the stone wall in her seventh-storey apartment "for quite a while" before she heard neighbours calling for people to evacuate.

"An hour after the quake, everyone is still outside waiting for safety in case there's an aftershock," says the journalist, who lives in Palos Grandes, a prime district in central Caracas which was among the hardest hit by the earthquakes.

Despite it being a weekday, many people were at home as the quakes struck on a national holiday commemorating the 1821 Battle of Carabobo, a decisive victory by Venezuelan independence leader Simón Bolívar against the Spanish colonial power.

Photos and videos emerging from the affected areas show some people in tears and others embracing out on the streets.

"There are people who are very sad, powerless because they couldn't get their pets out," Kolster says.

"Others tried to get their cars out of the building basements, fearing an aftershock might make things worse."

Calls for help could be heard from the rubble of a collapsed building nearby, she adds.