Fifty-one women in the Democratic Republic of Congo have accused international aid workers in the eastern city of Beni of demanding sexual favors from them in return for jobs or under threats that their contracts would be terminated if they refused.

According to an investigation by The New Humanitarian and the Thomson Reuters Foundation, several men working for aid organizations including the World Health Organization (WHO), UNICEF, Oxfam, Doctors Without Borders (MSF), World Vision, ALIMA, and the International Organization for Migration (IOM) were involved in the sexual exploitation and abuse of the women.

UN Secretary-General Antonio Guterres, who has been made aware of the allegations, has called for them to be "investigated fully."

Drugged, ambushed and locked up

The women, who work as cooks, cleaners, and community outreach workers, said they were drugged with drinks, ambushed in offices and hospitals and locked in rooms by men they identified as aid workers. More than 15,000 people were based in Beni and surrounding towns during the 2018 to 2020 Ebola operation.

According to the women, the abuses occurred back in March. They said they had not reported the incidents at the time for fear of losing their jobs or other reprisals, or out of shame.

Kahambu, one of the victims, told DW: "With the fight against Ebola, it was not easy to get a job. It was all about sex. What we did as an assessment test was just eyewash. People were taken even before they had taken the test. Before the hiring test, the bosses called us and offered us to sleep with them. If you turned them down, you were not hired for the job."

Some of the women even got pregnant Kuhambu told DW. "There are also some who have been infected with sexually transmitted diseases like AIDS because most of the helpers were sick. This is the case of a mother who worked with us. She was married but lived far away from her husband, she had slept with one of our bosses, recently she was diagnosed HIV positive."

Another victim called Kavugho told DW: "I had difficulties when I wanted to hand in my letter before the entrance exam. But the boss had given me an appointment at the hotel, he asked me to come and drop my letter off at the hotel in the evening around 8 p.m. I should have done that in the office."

Therese Mema Mapenzi, the director of Centre Olame Bukavu (COB), a Catholic women's organization, has condemned the sexual harassment of the women. "It prevents women from working freely and being engaged in organizations and in professional activities," she said.

WHO at the center of attention

At least 30 women said WHO workers were involved. WHO, which deployed more than 1,500 people to take part in the government-led operation to control the outbreak, said it was reviewing a "small number" of sexual abuse or exploitation reports in Congo.

"We would not tolerate such behavior by any of our staff, contractors or partners," said WHO spokeswoman Fadela Chaib.

COB says it would be ready to collaborate with WHO to denounce the cases but fears for the safety of the women.

"In many cases here in the DRC, we have seen the victims of sexual harassment and sexual violence not well protected," Mapenzi told DW.

"Whenever they denounce the people who have raped them, who are very powerful, instead of being protected by the justice system, they are condemned by the justice system itself," she said.

Does 'zero tolerance' policy work?

World Vision and ALIMA also said they would undertake an inquiry. Spokespeople for IOM, MSF, UNICEF and Congo's Health Ministry said they had no knowledge of the accusations, and several said they would need more information to take action.

Oxfam said it did "everything in our power to prevent misconduct and (to) investigate and act on allegations when they arise, including supporting survivors."

Although the women did not know all of the men's nationalities, they said some came from Belgium, Burkina Faso, Canada, Ivory Coast, France and Guinea.

The men also approached them outside Beni's main supermarkets, in job recruitment centers, or outside hospitals, they said. Local boys and young men were paid to procure women, according to a recruiter at an international NGO.

WHO and most of the aid groups facing the allegations said they had policies in place to prevent and report abuse or exploitation. The UN has a zero-tolerance policy.

Read more: The Oxfam scandal is just one aspect of the aid industry's ugly power problem

Years of sexual abuse and exploitation

But such reports of sexual abuse keep coming to light in Africa.

The Associated Press found that of the 2,000 sexual abuse and exploitation complaints made against UN personnel worldwide between 2005 and 2017, more than 700 occurred in Congo.

In September, the UN launched an investigation into allegations of sexual abuse and the exploitation of women by members of its staff in Uganda's Karamoja region.

In 2016, nearly 100 women and girls in Central African Republic accused UN peacekeepers of rape, sexual abuse and exploitation. Half of the ultimately 130 allegations were dismissed. An internal UN report detailed blunders in the investigations.

'An accountability problem'

"There is an accountability problem," says Lewis Mudge, the Central Africa director at Human Rights Watch, who has researched sexual violence committed by peacekeepers in the Central African Republic in the last years.

According to him, UN peacekeepers are not accountable under national legislation for any crimes they commit. "If a crime is committed, they are only accountable back in their home jurisdiction," he says.

The problem is, says Mudge, that this kind of immunity allows perpetrators to get away with crimes they have committed, which can go as far as murder.

"I think it is appropriate and right for the UN to say we have zero tolerance for sexual exploitation and abuse, but at the end of the day, there is very little the UN agencies can do with regards to peacekeepers besides sending them home and hope that the troop-contributing country will hold them to account," says Mudge. He says this happens only sporadically.

In 2014, almost 100 girls in the Central African Republic said they were sexually abused by international peacekeepers. The UN announced an investigation into allegations of rape and assault.

In 2011, several Oxfam staff were accused of sexual exploitation and abuse of women believed to be prostitutes in Chad in 2006.

In 2002, aid workers for more than 40 agencies, including the UNHCR and Save the Children in West Africa, were involved in extensive sexual exploitation of refugee children, offering food rations in return for favors.

Zanem Nety Zaidi and Sudi Mnette contributed to this article