By Daphne Psaledakis

WASHINGTON (Reuters) -The United States on Monday imposed visa restrictions on 100 Nicaraguans affiliated with the Nicaraguan National Assembly and judicial system, increasing pressure on the government of President Daniel Ortega as Washington warned of further action.

Scores of prominent Nicaraguans, including six who planned to challenge Ortega’s bid for a fourth consecutive term in office, have been arrested in recent weeks. Many have fled abroad.

Monday’s move targeted those who “helped to enable the Ortega-Murillo regime’s attacks on democracy and human rights,” U.S. Secretary of State Antony Blinken said, including through the arrest of 26 political opponents and pro-democracy advocates and the passing of what he said were repressive laws.

“The United States will continue to use the diplomatic and economic tools at our disposal to push for the release of political prisoners and to support Nicaraguans’ calls for greater freedom, accountability, and free and fair elections,” Blinken said in a statement.

The statement did not name the Nicaraguans hit with visa restrictions in the action.

International pressure has mounted on Nicaragua, with Ortega’s crackdown on the opposition described by Washington as a “campaign of terror” that the United Nations said meant November elections are unlikely to be free or fair.

(Reporting by Daphne Psaledakis and Doina Chiacu; Editing by Mark Heinrich)