Burundian authorities must investigate allegations that state security officials tortured 12 opposition politicians during the country's recent elections, Amnesty International said on Monday.
The organization's briefing paper A Step Backwards details how the individuals were slapped, kicked and hit, at times with batons, all over their bodies.
Some reported being threatened with death and, in one case, part of a detainees ear was cut off while being held by Burundi's National Intelligence Service (SNR) at their headquarters in Bujumbura between 23 June and 5 July.
"Reports of torture in Burundi have decreased in recent years, and its re-emergence is a very troubling step backwards," said Erwin van der Borght, Africa Programme Director at Amnesty International.
"It is unacceptable if members of the state security services get away with such heinous acts and if the investigation confirms individuals have committed crimes they should be prosecuted."
The 12 were arrested and most were charged with security related offences in connection with a series of pre-election grenade attacks, many of which appeared to target the ruling party.
Those tortured were opposition party members, some in leadership positions, within their parties. During SNR interrogations, suspects were asked about their party structures, colleagues and alleged plans to destabilize national security.
The SNR has denied the allegations of torture. The SNR's Legal Advisor told Amnesty International that any marks on the bodies of those concerned were the result of resisting arrest.
The SNR's explanation is inconsistent with the facts documented in A Step Backwards.
The Burundian authorities are yet to open a criminal investigation violating their obligations under national and international law. Torture was criminalized in Burundi's 2009 Penal Code.
"President Pierre Nkurunziza's inauguration on 26 August offers an opportunity for the Burundian government to commit to ending impunity," said Erwin van der Borght.
"The President must publically condemn torture and declare that any official, including SNR agents committing, ordering or consenting to torture will be prosecuted regardless of their rank."
Amnesty International has called on the Burundian government to ensure future compliance of the SNR and other officials with international human rights law and Burundian law.