The AU rights investigators said it was “necessary that, apart from strengthening AU human rights monitors and military observers, an international police mission is deployed.”
Last year the AU proposed a 5,000-strong peacekeeping force but the pan-African bloc buckled in the face of opposition from Bujumbura.
Hundreds have been killed and a quarter of a million people have left Burundi since President Pierre Nkurunziza’s controversial decision in April 2015 to run for a third term, a vote he won in July.
Anti-government protests were brutally quashed and killings and attacks have become a regular feature in the troubled country as the political crisis grinds on.
The AU said the police would help boost security and ensure “protection of people in those areas most affected by violence and which continue to witness it.”
The report, from the African Commission on Human and Peoples’ Rights, was presented to the AU earlier this month but only released publicly on Friday.
The AU investigators also called for the “reopening of the various independent radio stations that were arbitrarily closed down” and to “reverse the collective closure of the 10 civil society organisations that play a key role in the promotion and protection of human rights.”
The report was based on a week-long mission in December 2015, during which time the investigators’ movement was limited due to “an eruption of major fighting” in the capital.
“The major consequence of these limitations is that the delegation could not establish the exact identity of the perpetrators of the human rights violations,” it admitted.
Many of the abuses detailed in the 58-page report were therefore based on existing media and rights reports.
A team from the office of the UN High Commissioner for Human Rights began a four-month investigation earlier this month.
The probe comes five months after the UN Human Rights Council in Geneva called for a team to be “urgently” sent there as concerns grow that Burundi risks descending once again into civil war.
Long-stalled peace talks aimed at solving the year-long crisis are due to begin in Tanzania on Saturday, but the main opposition group has not been invited, demolishing hopes of a deal.