The United States on Wednesday imposed visa restrictions on more than 250 members of the Nicaraguan government and levied sanctions on three Nicaraguan entities in retaliation for "repressive actions" and a failure to stem migrant smuggling through the Central American country.

Senior administration officials told reporters that the officials subject to visa restrictions included police and paramilitary officials, prosecutors, judges and public higher education officials.

At the same time, the Departments of State, Homeland Security, and the Treasury issued a joint alert to notify airlines and travel agents about the ways smuggling and human trafficking networks are exploiting legitimate transportation services to facilitate illegal migration to the United States through Nicaragua.

"Actions by the Nicaraguan government are of grave concern. President Daniel Ortega and Vice President Rosario Murillo have put in place permissive-by-design migration policies," the Department of Homeland Security said in a statement.

The Nicaraguan government did not immediately respond to a request for comment.

Increasingly migrants have been flying into Nicaragua and then heading north overland to the U.S.-Mexico border as some smugglers have promoted the route through social networks.

Many migrants in recent years have started their journeys in Brazil or other South American countries, but flying into Nicaragua avoids the often perilous journey through the jungle region known as the Darien Gap on the Colombia-Panama border.

The administration of President Joe Biden, a Democrat, has struggled with record numbers of migrant crossings at the U.S.-Mexico border and, as he runs for reelection in November, voters have increasingly said that immigration is a top concern.

Senior Biden administration officials told reporters on a Wednesday conference call that sanctions would be levied against a Russian training center operating in Managua since October 2017 that enabled anti-democratic behavior and repression.

A press release from the Treasury Department said Nicaragua was one of Russia's "main partners" in Central America and the training center provided specialized courts to the Nicaraguan National Police (NNP), which the statement called "a repressive state apparatus, carrying out extrajudicial killings, using live ammunition against peaceful protests, and even participating in death squads."

In addition, the Treasury Department imposed sanctions on two gold companies it said were "government affiliated."

Gold is Nicaragua's top commodity export, the Treasury announcement said, and "this action aims to degrade the ability of the Ortega-Murillo regime to manipulate the sector and profit." Reuters was not immediately able to reach the companies for comment.

Migrant apprehensions on the border halved from December to March, according to U.S. government data, in part because of increased enforcement by Mexican authorities, U.S. Homeland Security Secretary Alejandro Mayorkas has said.