Burundian girls and women, with perceived links to political opponents, have been raped by police officers, officials of the national intelligence service (SNR) as well as men belonging to the youth wing of Burundi's ruling CNDD-FDD party since unrest began to flare there in April 2015, a human rights group has alleged.

Burundi's two-year long crisis has killed thousands of people and pits supporters of President Pierre Nkurunziza against those who say that his re-election in July 2015 for a third term violated the nation's constitution.

SOS-Torture Burundi has identified some 20 victims of sexual violence between 2015 and 2016, who sought refuge in neighbouring countries.

The organisation this week said it intends to hand victims' testimonies to a group of lawyers representing families of victims of killings and torture in Burundi before the International Criminal Court (ICC). The lawyers' collective is hopeful the ICC may launch an official investigation into alleged crimes against humanity committed in the small East African country.

In SOS-Torture Burundi's latest report, rape survivors testified about their ordeal. While the report does identify victims' identities to protect them, the rights organisation said the victims of sexual violence linked to the crisis "turned out to be mainly of Tutsi ethnicity", a minority group in the country.

Victims were attacked in their homes, or during their incarceration at the SNR, in police cells or after arbitrary arrests by the Imbonerakure.

Some of these victims have been infected with HIV/AIDS while others have had unwanted pregnancies and raised their children in spite of the trauma experienced. Another category of victims suffered physical injuries following their assault.

"The testimonies also reveal that victims were humiliated because they were raped in front of their children, others were forced to witness the rape of their daughters, but also women were raped after being forced to watch the assassination of their husbands," SOS-Torture Burundi said in its report.

No investigation has been opened following victims' rapes, the organisation said.

"SOS-Torture Burundi would like to emphasise that rape is a weapon of war which is also advocated by the Imbonerakure militia, as evidenced by a video posted a few weeks ago," the organisation added in reference to a shocking video released last month.

The footage evidenced the use of targeted rapes as a weapon by members of the Imbonerakure. While doing so, the young men sing a song calling for the intimidation of political opponents and an incitement to rape, with verses that say, "Impregnate the rivals (opponents) so they can give birth to Imbonerakure".

Following the release of the video, the ruling CNDD-FDD published a communiqué in which it appears to distance itself from its militia.