In Tuesday’s televised address, Vice-President Nicolas Maduro announced that the president had passed away “after battling a tough illness for nearly two years”.
“We have received the toughest and tragic information that… Comandante President Hugo Chavez died today at 16:25 (20:55 GMT),” he added.
The Vice-President also called on the nation to close ranks after its leader’s demise.
“Let there be no weakness, no violence. Let there be no hate. In our hearts there should only be one sentiment: Love.”
He promised to maintain Mr Chavez’s “revolutionary, anti-imperialist and socialist legacy”.
Hugo Chavez had been struggling with cancer for more than a year, undergoing several operations in Cuba.
Crowds of supporters gathered outside the hospital where the leader died, chanting “We are all Chavez!”
A self-proclaimed revolutionary, Mr Chavez was considered to be a controversial figure in Venezuela and on the world arena. Having proclaimed himself as a foe of the USA, he inspired a left-wing revival across Latin America.
Following his death, Mr Maduro will temporary execute duties of the president until an election is held within 30 days, Foreign Minister Elias Jaua said.
“It is the mandate that Comandante President Hugo Chavez gave us,” Mr Jaua told state television, adding that Mr Maduro would take part in the election as the candidate of the governing United Socialist Party (PSUV).
However, it was not immediately revealed when the election would take place, BBC writes.
Because of being seriously ill Mr Chavez hadn’t taken the oath of office after he was re-elected for a fourth term in autumn.
The exact nature of the president’s illness was never officially disclosed, causing numerous speculations about his health, as he had not been seen in public for several months.
Venezuela has declared a week of mourning after the death and his body will lie in state until a funeral on Friday.
Schools and universities are closed in order to grant supporters a chance to pay their respects to the passed away president.
Opposition leader Henrique Capriles, defeated in October’s election, urged the government to “act in strict accordance with its constitutional duties”.
He also offered his condolences to Mr Chavez’s family, saying “we were adversaries, but never enemies”.
The US described the death of Mr Chavez as a “challenging time”, reiterating its readiness to support the Venezuelan people and demonstrating its interest in developing a constructive relationship with Caracas.
“As Venezuela begins a new chapter in its history, the United States remains committed to policies that promote democratic principles, the rule of law, and respect for human rights,” said a statement from the White House.
Russia’s permanent representative to the UN, Vitaly Churkin, offered his condolences to Mr Chavez’s family, adding that the latter had been a great politician, for his country, for Latin America and the world.
Amadou Boudou, the vice-president of Argentina, expressed his “great sorrow for the death of Venezuelan President Hugo Chavez”, stressing that sympathy was felt across the region.
“There is great pain in all of America,” he said. “He was one of the best. Farewell, Commander.”