Venezuela's government has told workers and students to stay at home as the country faces a second day without electricity.
Hospitals, public transport, water and other services have been affected.
The capital, Caracas, was first plunged into darkness on Monday. Power was restored four hours later, before a second blackout struck.
A days-long nationwide power cut earlier this month prompted looting and desperation in parts of the country.
President Nicolás Maduro's government blames the power cuts on an “attack” by the opposition, led by Juan Guaidó.
The opposition cites two decades of underinvestment and corruption by the socialist government as the cause of the power outage.
“Nothing is working,” Yendresca Munoz, a 34-year-old bank analyst living in Caracas told Reuters news agency. “During blackout days you can't do anything at all. There's no internet, no access to cash.”
Other big cities, including Barquisimeto, Maracaibo in the west of the country, have also been reportedly affected.
On Twitter, Mr Guaidó said: “When our people need certainty in the middle of another unsettling blackout, how can they go on repeating excuses of an ‘electricity war' and sabotage?”
Since January, the opposition leader has been locked in a power struggle with Mr Maduro's government, which is grappling with a severe economic crisis.
Last week, Mr Guaidó's chief of staff was arrested on terrorism charges in another escalation of the political…
