The World Health Organization issued its plan on Thursday to prevent any further misconduct by aid workers deployed in its field operations after WHO staff were caught up in a major sexual abuse scandal in the Democratic Republic of Congo.

Some 83 aid workers, a quarter of them employed by the WHO, were involved in sexual exploitation and abuse during the country's massive Ebola epidemic from 2018-2020, an independent commission said last month.

WHO Director-General Tedros Adhanom Ghebreyesus vowed to ensure that the affair and the victims' suffering would be "the catalyst for a profound transformation of WHO's culture."

There will be no opportunity for sexual exploitation to occur, no impunity if it does and "no tolerance for inaction," he said in a statement on the WHO's management response plan.

"WHO will investigate potential acts of negligence by senior staff that may amount to misconduct as recommended by the independent commission," agency spokesperson Tarik Jasarevic told a U.N. news briefing on Friday.

The WHO had already terminated the contracts of four staff identified as perpetrators and was referring allegations to Congolese authorities for criminal proceedings, he said.

Major donors, led by the United States and European Union, have urged WHO to launch a deeper external investigation demanding how the scandal was allowed to happen, diplomats told Reuters last week.

The pressure seems to have paved the way for further scrutiny, although one Western diplomat told Reuters on Friday: "This isn't over."

"WHO is requesting UN OIOS (Office of Internal Oversight Services) to carry out a review of, and where necessary, further investigation into all cases of alleged SEA (sexual exploitation and abuse) identified by the Independent Commission, including those in which they identified an alleged WHO perpetrator," the statement said.

A separate team of external investigators will oversee an inquiry into "alleged managerial misconduct in respect of failure to initiate investigation procedures", it said.

Tedros, who visited Congo 14 times during the Ebola epidemic, told reporters last month when the commission unveiled its full findings that no one had raised the allegations.

He is believed to be seeking a second five-year term in WHO's election next May, but declined to comment on Thursday.

As first reported by Reuters last week, the WHO said that it was deploying experts to 10 high-risk countries, including Afghanistan and Ethiopia, to prevent sexual exploitation. In the past week nearly 40 employees of WHO and U.N. partner agencies have been trained in prevention, it said.