Thousands of people descended on central Caracas on Monday evening, some walking for miles from slums on the mountains surrounding the city, towards the presidential palace.
Protests erupted in the Venezuelan capital the day after President Nicolás Maduro claimed he had won.
The opposition has disputed Mr Maduro’s declaration of victory as fraudulent, saying its candidate Edmundo González won convincingly with 73.2% of the vote.
Opinion polls ahead of the election suggested a clear victory for the challenger.
Opposition parties had united behind Mr González in an attempt to unseat President Maduro after 11 years in power, amid widespread discontent over the country’s economic crisis.
