CARACAS, Venezuela — One day after President Nicolás Maduro of Venezuela declared re-election victory, the Trump administration on Monday placed new sanctions on the crisis-ridden country, and nations across the region refused to recognize the election result.

President Trump signed an executive order on Monday afternoon imposing the new penalties, which would bar United States companies or citizens from buying debt or accounts receivable from the Venezuelan government. The order extends to Petróleos de Venezuela, the government-owned oil company that is the parent of Citgo Petroleum Corporation.

The measures were devised to close off an “avenue for corruption” that senior administration officials said they had observed Mr. Maduro and members of his government using to enrich themselves. The officials, who described the sanctions on the condition on anonymity because they were not authorized to be named discussing them, declined to reveal any specific instances.

The Lima Group, an association of mainly Latin American nations that has aimed to put pressure on Mr. Maduro’s government, issued a statement on Monday saying that it “did not recognize the legitimacy of the electoral process” and that the vote had not “met with the international standards of a democratic, free, just and transparent electoral process.”