CARACAS, Venezuela -- Tensions escalated here on Tuesday as the newly elected president, Nicolás Maduro, and his opponent blamed each other for the violence that the government said had left seven people dead, and Mr. Maduro accused the United States of being behind that violence.
The new president vowed to crack down on protests and said he would block a march called by his opponent, Henrique Capriles Radonski, to demand a recount of the vote. Mr. Capriles claims he is the real winner of the extremely close election on Sunday and has refused to recognize the result.
Mr. Capriles responded to Mr. Maduro on Tuesday by calling off the march to the headquarters of the National Electoral Council, which had been planned for Wednesday, saying he had received information that the government planned to infiltrate the march and cause violence. He called on his followers instead to bang pots at their homes in a traditional Venezuelan protest.
Mr. Maduro was declared the winner of Sunday's election with 50.8 percent of the vote, to 49 percent for Mr. Capriles, according to the current government count. The tally has Mr. Maduro ahead by about 270,000 votes, out of 14.8 million cast, although not all votes have been counted. Among those outstanding are votes from Venezuelans living in foreign countries, who tend to vote for the opposition.
Mr. Maduro is to complete the six-year term of President Hugo Chávez, who had cancer and died March 5. His new term began in January.
In an extraordinary day of charges and countercharges, Mr. Maduro cut into regular television and radio programming three times with special national broadcasts that all stations are required to carry.
Each time he angrily criticized Mr. Capriles, sometimes working himself into what seemed to be near hysteria, shouting until he was nearly out of breath, often stabbing his finger directly at the camera. He compared the opposition to Nazi Germany, accused them of planning a coup, and said they hoped to bring about a civil war like those in Libya and Syria.
"The march to the center of Caracas will not be permitted," Mr. Maduro said in his first broadcast, from a government-run health clinic. "I will use a hard hand against fascism and intolerance. I declare it. If they want to overthrow me, come and get me. Here I am, with the people and the armed forces."
He said five people died at opposition protests on Monday in different parts of the country, and, pointing a finger at the camera, he said Mr. Capriles was responsible. Mr. Maduro later raised the death toll to seven, but the number of deaths related to the protests could not be independently confirmed.
At an afternoon news conference, Mr. Capriles said the government had given T-shirts to people who would attend Wednesday's march and then carry out violent acts. "Their agenda is violence," he said. "Our agenda is peaceful protest."
Mr. Capriles also questioned the government claims that all the deaths cited were associated with the protests.
In a second broadcast, from an office of the government-run oil company, Petróleos de Venezuela, Mr. Maduro lashed out at Washington.
"The United States Embassy has financed all the acts of violence in this country," he said, adding that violent groups were directed by two American military attachés whom he had expelled the day that Mr. Chávez died. He accused another American Embassy employee of plotting to sabotage the nation's electrical system.
In each broadcast, Mr. Maduro returned to the theme of threats to his government. At one point he demanded that television stations choose sides. "Decide who you are with, with the country and peace and the people, or are you going to go back to be with fascism?" he shouted.
A United States State Department spokesman said in a written statement, "We continue to completely reject the Venezuelan government's claim that the United States is involved in any type of conspiracy to destabilize the Venezuelan government or to harm anyone in Venezuela."
The third time Mr. Maduro broke into regular television and radio programming, he cut off the broadcast of Mr. Capriles's news conference. Speaking from a hospital, he told his supporters to play loud music and shoot off fireworks each night to drown out the opposition's pots and pans protest.
In his news conference, Mr. Capriles said that his campaign had received information on thousands of voting irregularities, including opposition witnesses who were forcibly removed from voting centers and voters intimidated by armed motorcyclists.
The government said that the seven people who were killed were supporters of Mr. Maduro. But the father of one of those killed, Ender José Bastardo, 21, disputed that account.
The Justice Ministry said that Mr. Bastardo, a mechanic, was among a group of people celebrating Mr. Maduro's victory in Cumanacoa, in eastern Venezuela, when they were attacked by a group that opened fire. Mr. Bastardo was killed and two other people were wounded.
But Mr. Bastardo's father, William Bastardo, 45, said he and his son were marching in a protest against Mr. Maduro's election, banging pots, when shots were fired from a nearby building. "I demand justice for my son," the father said at the morgue in the nearby city of Cumaná, "and that peaceful protest be respected."
Paula Ramón and María Eugenia Díaz contributed reporting from Caracas, and María Iguarán from Cumaná, Venezuela.
This article originally appeared in The New York Times.