Some African Union peacekeepers allegedly raped Somali women and gave them food and medicine to disguise the abuse.
A report by Human Rights Watch (HRW) documented the case of at least 10 women and girls, including a 12-year-old, who claimed they were raped by the soldiers in 2013 and 2014.
"Some of the women who were raped said that the soldiers gave them food or money afterwards in an apparent attempt to frame the assault as transactional sex," the report said.
The rapes were said to have taken place mainly at the African Union Mission in Somalia (AMISOM) bases in the capital Mogadishu, where women went to ask for assistance.
"Where this case is particularly shocking is the direct use of humanitarian assistance to lure these women in," Laetitia Bader, one of the report's authors, told Reuters.
"These were displaced women coming in to get medical assistance and it's when they are in the outpatient clinics that they get approached by a Somali intermediary who says: 'Why don't you come back to the base? We'll give you medication,'" Bader said.
HRW also interviewed 14 women and girls who claimed they were routinely paid $5 (£3) a day to have sex with the peacekeepers.
"Somali women having paid sex with soldiers have been able to obtain AMISOM badges allowing them easy access in and out of what should be highly secure military zones," the report said.
Only two women interviewed by HRW filed a report, while the others didn't, as they feared they would be persecuted.
AMISOM's spokesman Eloi Yao said the allegations against the troops will be "taken very seriously. Any AMISOM personnel found guilty of any such crimes will be dealt with appropriately".
African Union soldiers were deployed in Somalia in 2007 to help quell the violent insurgence of militant group al-Shabaab.
The soldiers, who come from nearby countries such as Uganda, Burundi and Kenya, cannot be prosecuted by the Somali government.