Presenting the report of a fact-finding mission, high commissioner for human rights Volker Turk told reporters in Geneva that crimes against humanity may have been carried out amid a climate of fear and mass arrests.

Testimony from senior Bangladesh officials and other evidence showed an official policy to attack and violently repress anti-government protesters and sympathisers, the report said.

The UN called for urgent further criminal investigation into the violations.

The protests began as a student-led movement against public sector job quotas but quickly morphed into a broader, nationwide uprising that forced then-prime minister Sheikh Hasina to resign and flee to India as the unrest peaked in early August.

Hasina, who had ruled Bangladesh since 2009, is being investigated on suspicion of crimes against humanity, genocide, murder, corruption and money laundering and Dhaka has asked New Delhi to extradite her.

Hasina and her party deny wrongdoing, while New Delhi has not responded to the extradition request.

Neither Hasina nor officials of her Awami League party could not be reached for comment on the UN human rights report.

The UN fact-finding mission visited Bangladesh at the invitation of the interim government led by Nobel Peace Prize winner Muhammad Yunus.

“Top echelons of the previous government were aware and were involved in the commission of very serious violations, including enforced disappearances, arbitrary detentions and suppression of the protests through violence” Turk told reporters.

When asked for examples of the worse violations found in the report, Turk told Reuters: “It’s a very brutal read; 78% of the over 1,000 people killed was by firing – military rifles, shotguns with pellets.”

Others suffered “horrific”, life-changing injuries, he added.