The U.S. government said Tuesday it would impose visa restrictions on individuals running charter flights into Nicaragua, flooding the Central American country with tens of thousands of U.S.-bound migrants, mostly from Haiti, Cuba and Africa.

The authoritarian government of Nicaraguan President Daniel Ortega, which has strained ties with the U.S., has in recent months allowed several little-known charter airlines and travel agencies to operate flights from Haiti, Cuba and other Caribbean airports to Nicaragua, according to Haitian and Nicaraguan civil aviation data.