A widespread power cut affecting much of Venezuela has continued throughout Friday ahead of planned protests on Saturday.
President Nicolás Maduro and the US-backed opposition trying to oust him have blamed each other for the outage.
Hospitals struggled to cope and at least one hospital patient died when her respirator stopped working.
The power cuts, which started on Thursday, have been caused by problems at a major hydroelectric plant.
Venezuela depends on its vast hydroelectric infrastructure, rather than its oil reserves, for its domestic electricity supply. But decades of underinvestment has damaged the major dams, and sporadic blackouts are commonplace.
Some parts of Caracas and the rest of the country have had their electricity supply restored and Venezuelans are now bracing themselves for a weekend of pro and anti-government protests.
Will the blackout affect protests?
Mr Maduro has accused the opposition of sabotage, which he described as a “new attack by enemies of the fatherland”, while his deputy Ms Rodriguez condemned an “imperial electrical war”.
Mr Guaidó hit back, urging Venezuelans to demonstrate on Saturday “against the usurping, corrupt and incompetent regime that has put our country in the dark”.
He said the blackout was the result of years of under-investment and told a gathering marking International Women’s Day that it could not be normal that “50% of hospitals in the country don’t have an electric plant”.
Mr Maduro has also called for a demonstration and tens of thousands of people are expected to participate in the two rallies.
However the BBC’s Will Grant in Caracas says the blackout has affected public transport and mobility in the capital city and may have an impact on turnout.
Why do blackouts happen in Venezuela?
Blackouts are nothing new in Venezuela. Critics say they have been getting worse since the nationalisation of the power grid in 2007. In 2016, the problem reached such a critical level that the government declared a 60-day nationwide state of emergency.
In an attempt to stem the country’s chronic power shortages, the government has periodically enforced controlled blackouts, where they would switch the power off for up to six hours at a time.
Critics say that far from helping, this has caused perishable food to go bad and crime to run rampant. And when unplanned blackouts – such as the latest one – have happened, officials have blamed a number of different outside forces, including animals such as iguanas entering hydroelectric substations.