GENEVA — The U.N. 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.

In a new report, the Geneva-based office says security and intelligence services “systematically engaged” in rights violations that could amount to crimes against humanity and require further investigation.

Citing “various credible sources,” the rights office said it estimated that as many as 1,400 people may have been killed in the protests between July 15 and Aug. 5 — the day longtime Prime Minister Sheikh Hasina fled to India amid the uprising.

Thousands more were injured in the weeks leading up to and after the protests, the report said.

Over 11,700 people were detained, the report said, citing information from security services. It said that about 12 to 13% of people estimated to have be killed — or as many as about 180 people — were children.

In some cases, “security forces engaged in summary executions by deliberately shooting unarmed protesters at point blank range,” it said.

U.N. human rights chief Volker Türk cited signs that “extrajudicial killings, extensive arbitrary arrests and detentions, and torture” were conducted with the knowledge and coordination of the political leadership and top security officials as a way to suppress the protests.

The U.N. fact-finding team was deployed to Bangladesh at the invitation of the country’s interim leader, the Nobel Peace laureate Muhammad Yunus, to look into the uprising and violent crackdown.

The team of investigators said the interim government has reportedly made 100 arrests in connection with attacks on religious and indigenous groups. The report said “many perpetrators of acts of revenge, violence and attacks on distinct groups apparently continue to enjoy impunity.”

The human rights situation in Bangladesh continues to raise concerns, the U.N. office said.