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.