MANAGUA, Nicaragua — President Daniel Ortega’s government is arresting his top challengers in the November elections in a sharp escalation of political repression in Nicaragua.

Authorities arrested two more presidential hopefuls on Tuesday — Félix Maradiaga, an academic and political activist, and Juan Sebastián Chamorro, an economist — after detaining Arturo Cruz and Cristiana Chamorro in the previous week. The roundup represented a clear challenge to the Biden administration, occurring around Vice President Harris’s visit to Central America and Mexico this week to promote good governance and find solutions to unauthorized migration.

Geoff Thale, president of the Washington Office on Latin America, an advocacy group, said the arrests were a signal to the Biden administration — “a message that plays to nationalist sentiment in the region, that the gringos aren’t going to push us around.”

The Chamorros are cousins and belong to the most storied political family in Nicaragua. Cristiana Chamorro’s mother, Violeta Barrios de Chamorro, defeated Ortega in the presidential race in 1990, ending the 11-year reign of the Sandinista movement that had triumphed in a 1979 revolution.

The U.S. government has slapped financial sanctions on a growing number of Nicaraguan political and security officials since a bloody government crackdown on nationwide protests in 2018. The Biden administration has continued that policy, targeting officials it says are corrupt and dismantling democratic institutions.

On Wednesday, the U.S. Treasury blacklisted four more prominent government supporters, including the head of the central bank, Leonardo Ovidio Reyes Ramírez, and Ortega’s daughter Camila, who helps manage a family-run TV channel. Ortega’s wife, Vice President Rosario Murillo, and several of their sons had already been sanctioned.

But the penalties haven’t moved Ortega to change course.

Julie Chung, the acting U.S. assistant secretary for Western Hemisphere affairs, called on Ortega’s government to release the detainees. The government’s crackdown “calls for an urgent international response,” she tweeted.

Murillo lashed out Wednesday at the Biden administration, saying the new sanctions were “illegal, arbitrary, coercive and unilateral.” She denounced the detained candidates as “traitors” seeking to launch a coup.

Maradiaga, 44, was arrested after being summoned for questioning Tuesday morning by the federal prosecutor’s office. Police said he was being investigated for allegedly inciting interference in Nicaragua’s affairs,” and organizing terrorist acts with financing from foreign powers.”

Maradiaga, a center-left politician, dismissed the allegations. “This is a political case,” he told reporters shortly before his detention. “What we have done is fight alongside the Nicaraguan people, and we will continue to do so.”

Later Tuesday, police arrested Juan Sebastián Chamorro, 49, at his home in Managua, the capital. He was detained for “acts that undermine the independence, the sovereignty and the self-determination” of Nicaragua, police said. Among his alleged misdeeds, police said, was “applauding the imposition of sanctions” on the country.

Chamorro, the former director of the opposition Civic Alliance coalition, said in a video released late Tuesday that he would “never accept any charge of treason from a dictatorship that has sold out Nicaragua.”

Authorities have also opened a treason investigation into Cruz, a former Nicaraguan ambassador who broke with Ortega and was detained on Saturday. He was ordered jailed for three months while the probe is underway. Cristiana Chamorro, a journalist and the leading candidate in the polls, is under house arrest amid government allegations of money laundering. She and Cruz say they are innocent.

Ortega, 75, is seeking a fourth consecutive term in the Nov. 7 election. Independent polls show his popularity has dropped to its lowest point ever in the wake of a devastating economic crisis and a rise in political repression.

“He is undermining the electoral process,” political analyst Eliseo Núñez said. “Ortega wants the opposition to be weakened in November.”

U.N. spokesman Stephane Dujarric said Wednesday that the arrests of the presidential candidates “can seriously undermine the public’s confidence in the democratic process ahead of the November general elections,” and called for their release.

Sheridan reported from Mexico City.

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