The United Nations human rights office on Wednesday estimated that up to 1,400 people may have been killed in Bangladesh over three weeks last summer in a crackdown on student-led protests against the now-ousted former prime minister.

Officials from Bangladesh's former government and security apparatus systematically committed serious human rights violations against protesters staging mass demonstrations last summer, the U.N. human rights chief said on Wednesday.

Former Bangladesh prime minister Sheikh Hasina and her government tried to cling on to power using systematic, deadly violence against protesters that could amount to "crimes against humanity", the UN has said.

The UN human rights chief says officials from former PM Sheikh Hasina's government and security services committed serious human rights violations. He said crimes against humanity may have been carried out.