World Health Organization (WHO) staff were among 83 aid workers who sexually abused women and girls while tackling the Ebola outbreak in the Democratic Republic of Congo, a report finds.
The abuses, which included nine allegations of rape, were committed by both national and international workers between 2018 and 2020.
The report comes after more than 50 local women reported sexual abuse.
WHO Director-General Tedros Adhanom Ghebreyesus said it was "inexcusable".
The 35-page report was produced by an independent commission following an investigation.
The commission, which interviewed dozens of women who had alleged they were offered work in exchange for sex, found that 21 of the 83 alleged perpetrators were employed by the WHO.
Local women were also allegedly plied with drinks, "ambushed" in hospitals, forced to have sex, and two became pregnant.
The WHO said it was terminating the contracts of four people who were still employed by the organisation and promised more measures would be taken.
Speaking at a news conference on Tuesday, Dr Tedros said the report made for harrowing reading and apologised directly to the victims and survivors.
"I'm sorry for what was done to you by people who are employed by WHO to serve and protect you," he said. "It is my top priority that the perpetrators are not excused, but held to account."
He said the responsibility ultimately rested with him and promised to help support and protect victims, while vowing to overhaul the WHO's structure and culture.
WHO Africa regional director Matshidiso Moeti also apologised to those who suffered "because of the actions of our staff".
The commission said it found "clear structural failures and unpreparedness to manage the risks of incidents of sexual exploitation and abuse" in the central African country.
It said this was partly because of the focus on eradicating Ebola.
More than 2,000 people died in the Ebola outbreak in DR Congo.
The WHO, which spearheaded global efforts to curb the spread of the outbreak, declared it over in June last year.