The 58-year-old president died on Tuesday after a two-year battle with cancer that was first detected in his pelvis. He had suffered multiple complications following his latest operation on December 11 and had not been seen in public since then.
The future of Chavez's self-styled leftist revolution, which won him passionate support from the poor but alienated opponents who called him a dictator, now rests on the shoulders of his preferred successor, Vice President Nicolas Maduro.
"In the immense pain of this historic tragedy that has affected our fatherland, we call on all the compatriots to be vigilant for peace, love, respect and tranquility," Maduro said.
"We ask our people to channel this pain into peace."
Maduro, a 50-year-old former bus driver and union leader, will be the government's candidate at a new presidential election that is likely to pit him against opposition leader and state governor Henrique Capriles.
The authorities said a new vote would be called within 30 days, but it was not immediately clear if that meant the election would be held within 30 days - or whether the date for the ballot would be announced within 30 days.
Military commanders quickly pledged loyalty to Maduro, who becomes caretaker leader until the new election.
Much of Caracas was quiet overnight, with streets deserted especially in richer parts of the capital. Most shops locked their doors as the news spread, fearing looting.
Despite having weeks to come to terms with their leader's likely demise, Chavez supporters were wrought with grief.
"He was our father," said Nancy Jotiya, 56, sobbing in Caracas' central Plaza Bolivar. "He taught us to defend ourselves. Chavismo is not over! We are the people; we will fight!"
Hundreds of emotional "chavista" loyalists gathered outside the military hospital where the president spent his last two weeks. A female TV reporter from neighboring Colombia was beaten up, and gunshots were fired in the air.
Messages of condolences for Chavez's death came from around the world, ranging from filmmaker Oliver Stone to U.N. Secretary General Ban Ki-moon and U.S. President Barack Obama.
Obama said his administration was interested in "developing a constructive relationship with the Venezuelan government."
Chavez easily won a new six-year term at an election in October and his death shocked millions of supporters who loved his folksy charisma, anti-U.S. diatribes and oil-financed projects to improve life for residents of long-neglected slums.
Critics, however, saw his one-man style, gleeful nationalizations and often harsh treatment of rivals as evidence he was a dictator whose misguided statist economics squandered a historic bonanza of oil revenues.
FUNERAL "TO RIVAL EVA PERON'S"
On Wednesday, Chavez's body will be transferred to a military academy where it will lie in state until his official funeral on Friday. Seven days of mourning will also be observed.
"The funeral of Chavez is going to rival Eva Peron's," said Daniel Hellinger, a U.S.-based Venezuela expert, referring to the beloved former first lady of Argentina who died in 1952 at the height of her popularity.
Chavez's death will test whether his leftist "revolution" can live on without his over-arching personality at the helm.
One recent opinion poll gave Maduro a strong lead over Capriles because he has received Chavez's blessing as his heir apparent, enjoys support among many of the working class and is expected to benefit from an inevitable surge of emotion.
Maduro has been a close ally of Chavez for years and would be very unlikely to make significant changes to the late president's policies, although he could at some point try to ease tensions with investors and the U.S. government.
Just hours before Chavez's death, however, Maduro alleged that "imperialist" conspirators had infected the president with cancer among a plethora of conspiracies with domestic opponents. The government never said what type of cancer Chavez had, but experts suspect it was a soft-tissue sarcoma.
A victory by Capriles would bring in much deeper changes and would be welcomed by business groups and foreign investors, although he would probably move cautiously in order to lower the risk of political instability and violence.
Venezuela has the world's largest oil reserves and some of the most heavily traded bonds, so investors will be highly sensitive to any signs of turmoil.
An opposition election win would upend alliances with Latin American governments that have relied on Chavez's oil-funded largesse - most notably communist-led Cuba, which recovered from financial ruin in the 1990s largely thanks to Venezuelan aid.
His health weakened severely just after his re-election on October 7, possibly due to his decision to campaign for a third term instead of stepping aside to focus on his recovery.
He was a garrulous figurehead for a global "anti-imperialist" alliance stretching as far as Belarus and Iran, and will be sorely missed by anti-U.S. agitators.
He alienated investors with waves of nationalizations and strict currency controls, often bullied his rivals, and disappointed some followers who say he focused too much on ideological issues at the expense of day-to-day problems such power cuts, high inflation and crime.
Chavez built a highly centralized system around his larger-than-life image and his tireless, micro-managing style created something close to a personality cult.
Maduro will now focus on marshalling support from Chavez's diverse coalition, which includes leftist ideologues, businessmen, and radical armed groups called "colectivos."
The vice president has mimicked Chavez's rabble-rousing style in recent weeks, peppering speeches with insults aimed at adversaries. Until recently, polls had shown Capriles would beat any of Chavez's proteges. But the naming of Maduro as Chavez's heir, and the outpouring of emotion that will accompany Chavez's death, have changed the picture.