"I'm tired of living in a country with such a dictatorship, I want to be free," said one protester, who asked not to be named due to worries of being imprisoned herself.
The rally was called by opposition politician Maria Corina Machado, who also urged the International Criminal Court -- which is already investigating alleged crimes against humanity in Venezuela -- to press for the release of what NGO Foro Penal says are more than 1,900 "political prisoners."
Most of the detainees were arrested in protests that followed Maduro's July election for a third consecutive six-year term, with his victory declared by state authorities seen as loyal to him. The opposition claimed the vote was fraudulent.
Fearing arrest, Machado has been in hiding since the election, while opposition presidential candidate Edmundo Gonzalez Urrutia has fled to Spain.
"Internationally, they have to take action," a woman at Sunday's protest told AFP. Her face was hidden by a mask marked by red lipstick, a symbol that represents the blood of the 28 people killed in the post-election unrest.
Similar demonstrations were held in other cities around the world, including Washington, Madrid and Buenos Aires.
The United States last week sanctioned 21 top Venezuelan security and cabinet officials, accusing them of involvement in a campaign of repression after Maduro's reelection.
Washington and the G7 had earlier recognized opposition candidate Urrutia as the rightful winner of July's vote, in a move that angered Caracas.
