Human Rights Watch says Burundi's intelligence services have tortured scores of suspected government opponents at their headquarters and in secret locations.

The rights group reported Thursday that abuses often have been carried out in collaboration with members of a pro-government youth militia group known as the Imbonerakure.

Burundi has been chaotic since April 2015, when President Pierre Nkurunziza announced plans to seek a third term that he ultimately won. Hundreds of people were killed as security forces tried to quell protests.

Human Rights Watch says agents of Burundi's national intelligence service have beaten detainees with hammers, driven sharpened steel rods into their legs and dripped melted plastic on them.

The right group urges the U.N. Security Council to deploy an international police force and set up a commission of inquiry.