Heads of state, including the presidents of Argentina, Uruguay and Bolivia visited Venezuela to mourn Chavez, well-known for his left-wing politics and staunch anti-Americanism.
Venezuelan Vice President Nicolas Maduro will continue to be interim president as he has since Chavez was hospitalized for cancer treatment. Venezuela's constitution requires an election to be called within 30 days. Maduro will run as the candidate of Chavez's socialist party.
The country's defense minister pledge military support for Maduro's candidacy. A constitutional mandate requires the armed forces play a nonpolitical role, however.
Henrique Capriles is the likely opposition candidate for presidency. He lost to Chavez in the last election in October.
Venezuela's constitution specifies that the speaker of the National Assembly, currently Diosdado Cabello, should assume the interim presidency if a president can't be sworn in.
But critics say the officials left in charge by Chavez before he went to Cuba in December for his fourth cancer surgery have not been assiduous about heeding the constitution, and human rights and free speech activists are concerned they will flaunt the rule of law. Many took to Twitter to cite Article 233 of the constitution, which they said establishes Cabello as the rightful interim president.
Many Venezuelans flocked to supermarkets and gas stations to stock up on supplies, preparing for turmoil following Chavez's death on Tuesday from cancer. Chavez was 58.
Just a few hours before announcing Chavez's death, Maduro virulently accused foreign and domestic enemies, clearly including the United States, of trying to undermine Venezuelan democracy. The government said two U.S. military attaches had been expelled for allegedly trying to destabilize the nation, and Maduro insisted that Chavez was purposefully "attacked" with cancer. He said a scientific commission would be set up to investigate.
There has been no word on any plans for an autopsy, and while the government has said Chavez suffered from cancer, it has never specified the exact location or type of cancer.
Many mourners Wednesday took their cue from Maduro, venting anger at Washington and accusing Venezuela's opposition of conspiring with far-right U.S. forces to undermine the revolution.
Venezuela and the United States have a complicated relationship, with Chavez's enemy to the north remaining the top buyer of Venezuelan oil. But Chavez's inner circle has long claimed the United States was behind a failed 2002 attempt to overthrow him, and he has frequently used anti-American rhetoric to stir up support. Venezuela has been without a U.S. ambassador since July 2010 and expelled another U.S. military officer in 2006.
U.S. State Department spokesman Patrick Ventrell denied Washington was trying to destabilize Venezuela and said the claim "leads us to conclude that, unfortunately, the current Venezuelan government is not interested in an improved relationship."
Ventrell added that the suggestion that the United States had a hand in Chavez's illness was "absurd." He hinted the U.S. could reciprocate with expulsions of Venezuelan diplomats.
Capriles, the youthful governor of Miranda state who lost to Chavez in October presidential election, was conciliatory in a televised address Tuesday. He is widely expected to run against Maduro.
Several incidents of political violence flared after Chavez's death.
A group of masked, helmeted men on motorcycles, some brandishing revolvers, reportedly attacked about 40 students on Tuesday who had been protesting for more than a week near the Supreme Court building to demand the government give more information about Chavez's health.
The assailants, who didn't wear clothing identifying any political allegiance, burned the students' tents and scattered their food just minutes after Chavez's death was announced.
Outside the military hospital, an angry crowd also roughed up a Colombian TV reporter.
Maduro and other government officials have railed against international media for allegedly reporting rumors about Chavez's health.
Chavez leaves behind a political movement in control of a nation that human rights activist Liliana Ortega, director of the nongovernmental group COFAVIC, describes as a badly deteriorated state where institutions such as the police, courts and prosecutor's offices have been converted into tools of political persecution and where most media are firmly controlled by the government.
The Associated Press contributed to this report.