The U.S. sanctions included the energy minister, vice-minister of finance and an entire government ministry, following Ortega's re-election to a fourth consecutive term on November 7.
U.S. President Joe Biden accuses Ortega of organizing a "pantomime" election in the Central American nation, and U.S. officials vow to work with allies to continue imposing further measures.
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"The United States is sending an unequivocal message to President Ortega, Vice President Murillo and their inner circle that we stand with the Nicaraguan people in their calls for reform and a return to democracy," Andrea Gacki, director of the U.S. Treasury's Office of Foreign Assets Control, said in a statement.
A senior State Department official, speaking anonymously, said last week that a sanctions announcement would be the first in a series of steps the U.S. government will "ramp up over time."
Previous sanctions imposed by Biden and his predecessor Donald Trump have had few results, yet analysts predict they could have much impact on the population.
Ortega has denounced the U.S. as "Yankee imperialists" and accused them of undermining Nicaragua's electoral process, which Cuba, Venezuela, Bolivia, Russia and other nations have all openly offered to recognize.
On Friday, the Washington-run Organization of American States (OAS) adopted a resolution saying Nicaragua's election lacked "democratic legitimacy." Yet, seven nations, including Mexico, Honduras and Bolivia, abstained from the vote.
The British Foreign Office said sanctions had been imposed on Murillo "for her involvement in the state-backed repression of demonstrations, the discrediting of independent journalists and the exclusion of opposition candidates from elections."
Murillo was already hit by U.S. sanctions in 2018.
Among those sanctioned by the United States on Monday were Salvador Mansell Castrillo, minister of energy and mines; Jose Adrian Chavarria Montenegro, vice-minister of finance and public credit; an ambassador, and several mayors and energy officials.
Treasury sanctions call for a freeze on U.S. assets of individuals or entities and prohibit Americans from doing business with them.
The British sanctions also targeted Nicaragua's attorney general, the Supreme Court of Justice president, and the president of the National Assembly, the Foreign Office said.