President-elect Nicolas Maduro further charged Tuesday that the violence was being bankrolled and directed by the United States, which said it wouldn't recognize his victory without a vote-by-vote recount demanded by Capriles.
It was not clear, however, whether the violence was as serious as Chavez's anointed successor claimed. Venezuela has an average of more than 40 homicides daily, one of the highest rates in the world, and the government offered almost no information on the deaths that Maduro blamed on "neo-Nazi gangs."
Capriles called the government assault a smoke screen to divert attention from his demand for a recount of every ballot from Sunday's election, which the National Electoral Council said Maduro won by 262,000 votes out of 14.9 million cast.
A number of opposition protests across Venezuela have turned violent, but apparently only after National Guard riot troops and police used tear gas and plastic pellets to turn back marchers converging on provincial offices of the electoral council.
While government officials complained of violence by Capriles' supporters, incidents of intimidation by gangs of pro-government forces, some armed, also occurred.
An Associated Press journalist witnessed a pro-government gang of motorcycle toughs rampage through Teques, seat of the state that Capriles governs. They tossed a firebomb into an opposition party office and smashed display cases and looted goods from a bakery they said was owned by a Capriles supporter.
In the western town of San Francisco in Zulia state, three journalists with the local newspaper La Verdad said they were arrested by motorcycle-borne National Guard troops and jailed overnight Monday because they had interviewed a family that the troops had harassed. Reporter Juan Jose Faria wrote that the troop's commander told the reporters the country was in the midst of a coup and that they were putschists.
Maduro accused opposition protesters of attacking government health clinics, a socialist party office and the house of electoral council President Tibisay Lucena on Monday, but the government provided no details. Like Chavez, Maduro has a history of making allegations he does not substantiate.
Meanwhile, Maduro's government announced that 15 countries had confirmed they were sending high-level delegations to Maduro's swearing-in on Friday. They included Bolivia, Ecuador, Nicaragua, Iran, China, Saudi Arabia, Qatar, Haiti, Uruguay and Argentina.
The potential for violent street confrontations in the capital Wednesday seemed to be headed off when Capriles called off a planned march to electoral council headquarters. That decision came after Maduro urged his supporters to take to Caracas' streets at the same time.
"Whoever goes out into the street tomorrow is playing the government's game," Capriles said at a news conference. "The government wants there to be deaths in the country."
The president-elect spent Tuesday on state TV at various events demonizing Capriles as "a murderer" and coup plotter. And he heaped accusations on Washington — always a popular target of Chavez, for whom Maduro served as foreign minister for six years.
"The (U.S.) embassy has financed and led all these violent acts," Maduro said during an appearance at the state-owned oil company PDVSA, which accounts for more than 95 per cent of Venezuela's exports.
The countries have been without ambassadors since 2010 and the latest U.S. charges d'affaires, James Derham, left the country Monday.
Maduro's rhetoric did not sound designed to encourage the rapprochement that he has told various visiting American politicians, most recently former New Mexico Gov. Bill Richardson, that he is seeking.
The State Department said Tuesday that it was "difficult to understand" why Venezuela's electoral commission had not honoured Capriles' recount call.
Capriles says Chavistas stole the election and provided reporters with some examples. At 283 polling stations, election monitors were forced to leave before vote counts, some at the point of a gun, he said. At one voting booth in the western state of Trujillo a total of 717 people voted when only 536 were registered, he said.
People marched in various provincial capitals Tuesday to demand a recount. In Barinas, Chavez's home state, troops fired tear gas and plastic pellets at protesters marching on the provincial headquarters of the electoral council. Opposition leaders reported 30 arrests and three minor injuries.
Barinas Gov. Adan Chavez is a brother of the late president, who succumbed to cancer March 5 after 14 years as president. The opposition blames Chavez for economic disarray, worsening power outages and rampant crime.
Interior Minister Nestor Reverol accused Capriles of numerous crimes, including insurrection and civil disobedience. National Assembly speaker Diosdado Cabello said criminal investigations should also be opened against two top Capriles aides, Lara state Gov. Henry Falcon and Carlos Ocariz .
The Chavistas have long used a loyal criminal justice system to repress the opposition, human rights groups say. A Capriles campaign aide, Leopoldo Lopez, is currently facing influence-peddling charges in a 15-year-old case that he calls part of an attempt to selectively silence a now-emboldened opposition.
Security analyst Adam Isacson of the Washington Office on Latin America said the rising tension increases chances that the government could arrest opposition leaders, although he wondered whether security forces would comply with a wave of arrest orders.
He said he was more concerned about "mob violence against opposition figures, and perhaps pro-government ones, too."
Chief prosecutor Luisa Ortega, who announced the death toll, said 135 people had been detained in protests, presumably on Monday.
That's when Capriles' supporters protested in Caracas and other major cities, including Barinas, Merida in the west, and Maracay in the central industrial heartland.
Ortega did not provide identities for the dead and injured or say where the violence occurred. She said the dead belong to the "working class." The state news agency, AVN, said three of the dead were from the state of Zulia and one each from Tachira and Sucre states. It said, in addition, that eight Cuban-run health clinics, three offices of the United Socialist Party of Venezuela and three state-run Mercal supermarkets were "burned."
Officials said one death involved a man in the capital's Baruta district supposedly shot by opposition supporters in front of a Cuban-run health clinic when he and others where chanting pro-Maduro slogans. The AP visited the scene and could not establish in interviews with neighbours whether the killing was politically motivated.
It did determine, however, that 45-year-old Jose Luis Ponce, a carpenter, was not killed near the clinic. The government later corrected its version to reflect that.
Reverol said the other shooting deaths were being investigated.
Capriles said the government is to blame for any violence.
People across the nation banged on pots and pans Tuesday night to demand a recount at a pre-arranged evening hour, just as they did twice on Monday at Capriles' request.
He called for such "cacerolazos" every evening this week until Friday, when he said the cacophony should coincide with Maduro's swearing-in.
Associated Press writers Vivian Sequera, Fabiola Sanchez and Christopher Toothaker contributed to this report from Caracas, and video journalist Marko Alvarez from Teques.Suggest a correction