The United States has imposed sanctions on two senior security officials in the Democratic Republic of Congo who are allied to President Joseph Kabila.
It accuses army Gen Gabriel Amisi Kumba and John Numbi, an ex-police chief, of threatening the country's stability by suppressing the opposition.
The men, who have not commented on the allegations, have had their assets frozen in the US.
There have been recent protests against the postponement of presidential polls.
The opposition accuses President Kabila of trying to cling on to power beyond the end of his term, which is due to expire in December.
The US treasury said Gen Amisi had commanded units which violently suppressed opposition protests in several provinces, including one last year in which more than 40 people died.
"Soldiers have used excessive force and lethal weapons during demonstrations and political rallies," the US treasury statement said.
Mr Numbi is said to have intimidated voters to secure victories for candidates affiliated to President Kabila in elections in March for governors.
"Numbi threatened to kill opposition candidates who did not voluntarily withdraw from the race, and on the same day these exchanges purportedly took place, three candidates withdrew," the US statement said.
US-based Human Rights Watch (HRW) welcomed the sanctions and called for more leaders to be targeted.
"For the greatest impact, the US should expand sanctions to include other senior government, security, and intelligence officials responsible for brutal repression over the past two years," HRW researcher Ida Swayer said.
Last week, more protests erupted in the capital, Kinshasa, after the electoral commission failed to announce a date for the election but said that it would not be possible to hold the polls in November.
The headquarters of three opposition parties were also torched.
HRW says at least 50 people died in the clashes with the police, but the interior ministry put the figure at 17, including three officers.
Meanwhile, TV channel CFTV, owned by opposition leader Vital Kamerhe, says its frequency has been revoked and given to a different operator.
The constitution bars Mr Kabila, who took power in 2001 following the assassination of his father Laurent Kabila, from running for office again in a country that has never had a smooth transfer of power since independence more than 55 years ago.
A government-backed effort to work out a solution to the political crisis, called a "national dialogue", has been boycotted by most opposition parties.