The US has imposed sanctions on Nicaragua's Vice-President Rosario Murillo, the wife of President Daniel Ortega, accusing her of corruption and serious human rights abuses.
She is believed to have held influence over a youth organisation that the US says engaged in extra-judicial killings, torture and kidnapping.
Sanctions were also imposed on the presidential couple's security adviser.
Ms Murillo has ruled Nicaragua jointly with Mr Ortega for more than a decade.
She is accused of controlling the police and the youth wing of the governing Sandinista Liberation Front.
On Tuesday, the US Treasury said it was using a new executive order issued by US President Donald Trump to punish Ms Murillo, accusing her of undermining Nicaragua's democracy.
Meanwhile her aide – and the president's security adviser – Néstor Moncada Lau was accused of carrying out orders by paying armed groups to attack protestors during months of anti-government disturbances earlier this year.
The sanctions will ban US individuals, banks and other entities from carrying out transactions with the pair, who will also have any assets that fall under US jurisdiction frozen.
Nicaragua has been through huge upheaval this year. In April, anti-government protesters demanded that the socialist president, Mr Ortega, step down over unpopular pension reforms.
However, he refused to negotiate and instead sent in the security forces.
Hundreds were then killed in the space of weeks.
Earlier this month, opposition activist Félix Maradiaga told the BBC that human rights in Nicaragua were at the "most severe crisis in generations".
Mr Maradiaga was forced to flee his country in July after receiving death threats.