"We need an office to work in, so very soon, and when we have the armed forces totally on our side, we'll go to find my office there in Miraflores. Very soon," Guaido told supporters, who chanted back: "Yes, you can!"
Demonstrators banged pots and sounded car horns at the protest in a square in the east of the capital. Many waved large banners calling on Maduro to go.
"The situation is very difficult, we are hoping that this government will change. We've had enough of this chaos!" said one of the demonstrators, Miguel Gonzalez.
"With courage and strength I asked you to believe in yourselves, that Venezuela would emerge from the darkness, that the end of the usurpation is very close," said Guaido, who is recognized as interim president by more than 50 countries.
Venezuela's state prosecutor, Tarek William Saab, meanwhile told reporters he would place Guaido under investigation for "his alleged involvement in the sabotage of the Venezuelan electricity system."
It is the first government move against the US-backed Guaido since his return to Venezuela last week after defying a travel ban to visit several allied South American leaders.
Maduro has blamed a devastating multi-day blackout plaguing Venezuela on US "sabotage" in the form of an electromagnetic attack on the country's main hydroelectric complex.
But critics have long pointed the finger at the government for failing to maintain the power grid.
Guaido, 35, is seeking to capitalize on public anger over the blackout, which has piled misery on a population suffering years of economic crisis and shortages of food and medicine under Maduro.
The youthful opposition chief -- locked in a power struggle with Maduro since declaring himself interim president on January 23 -- has branded the socialist leader a "usurper" over his re-election in May, widely dismissed as neither free nor fair.
Outlining the case against Guaido, Saab said the opposition leader had disseminated a series of messages that have "stoked violence." "At this moment he appears as one of the intellectual authors of this electrical sabotage and is practically calling for a civil war in the middle of this blackout."
The US kept up the pressure on Tuesday, with its special envoy on the crisis, Elliott Abrams, saying Washington would soon impose "very significant additional sanctions" on institutions doing business with Maduro's government.
Prompted by Guaido's urging, the opposition-dominated National Assembly declared a "state of alarm" on Monday to pave the way for the delivery of international aid, 250 tons of which has been stuck for a month at Venezuela's borders with Colombia and Brazil.
However, with Maduro controlling the military and security services -- which are currently preventing aid from entering the country -- he has no means of enforcing it.
Maduro used the military to begin distributing food, water and other assistance in several districts on Tuesday.
Marshalled by security forces, crowds formed impatient lines at water trucks in some areas, as they waited to fill containers. But tensions were running high amid the shortages.
"I heard a lot of shooting," said Barboza, adding that a local bakery and a tire shop were looted.
The blackout has left millions without running water. Many people lined up to buy bottled water in Caracas supermarkets, but most are reduced to desperate means -- besieging fountains in public parks and any available water sources around the capital.
Maduro had called for armed grassroots groups known as "colectivos" to hit back against what he called attacks encouraged by the US against the country's electrical grid.
"The time has come for active resistance," he said in a speech late on Monday.
The opposition argues the colectivos have been armed by the government and act as militia.
Power has been restored to some areas since the weekend but service has been intermittent and the power often drops out. Businesses and schools remained shuttered on Tuesday on Maduro's orders, as they have been since the blackout began.
As the situation worsened, US Secretary of State Mike Pompeo announced Washington is withdrawing all its remaining personnel from the US embassy in Caracas. All non-emergency staff were ordered to leave on January 24.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)