KINSHASA (Reuters) - The United States on Thursday imposed sanctions on the top military adviser of Democratic Republic of Congo President Joseph Kabila, increasing pressure on his government over election delays and alleged human rights abuses.

The move follows travel bans and asset freezes announced on Monday by the European Union against nine Congo nationals and aimed at pushing Congo’s government to hold an election to replace Kabila by the end of the year.

Congo has repeatedly denounced sanctions by the EU and U.S. as unjustified and illegal, and has threatened diplomatic retaliation.

The U.S. Treasury Department placed General Francois Olenga on a list of “specially designated nationals”, freezing any assets he has in the U.S. and barring Americans from engaging in financial transactions with him.

It was not immediately clear whether Olenga actually possesses assets within U.S. jurisdiction.

In a statement, the Treasury Department said Olenga oversees elite Republican Guard forces that have threatened critics of Kabila and arbitrarily arrested and executed Congolese citizens.

“This action against Olenga sends a strong message that continued acts of violence, aggression and suppression by the Congolese military against its own citizens are unacceptable,” John E. Smith, director of the Treasury Department’s Office of Foreign Assets Control, said in a statement.

The Congolese government denies that it uses excessive force.

The Treasury Department also imposed sanctions on Safari Beach, a resort owned by Olenga on the outskirts of Congo’s capital Kinshasa.

Neither Olenga nor the Congolese army’s spokesman was immediately available to react to the announcement. Information Minister Lambert Mende, who was himself blacklisted by the EU this week, said he was not aware of the measures targeting Olenga.

Kabila, in power since 2001, refused to step down after his mandate expired in December. Under a deal struck with his opponents, an election must take place by the end of 2017 but the process remains stalled due to delays registering voters.

Security forces killed dozens of protesters during anti-Kabila demonstrations last year, raising fears of a slide back toward civil wars of the turn of the century that cost millions of lives.

Last year, the U.S. sanctioned five Congolese officials for alleged human rights violations, including the head of national intelligence and the then interior minister.

The U.S. was an outspoken critic of Kabila and other entrenched African leaders under former President Barack Obama but has kept a lower profile on the continent since Donald Trump entered office.

Olenga fought alongside Kabila’s father, Laurent, in the rebellion that overthrew longtime leader Mobutu Sese Seko in 1997.