The African Union force fighting in Somalia is reported to be investigating the alleged gang rape of a Somali woman by its soldiers.
The woman alleges she was abducted, drugged and then repeatedly raped earlier this month by soldiers from both the national army and from AMISOM, the 17,700-strong African Union force that supports the internationally backed government.
The case has prompted outrage in the capital Mogadishu.
"AMISOM is aware of the allegations levelled against its troops," the force said in a statement on Thursday.
A joint AMISOM and Somali army team has been set up "to investigate the matter and appropriate action will be taken once the facts of the case have been established," the AU statement added.
The AU mission "strongly condemns ... sexual abuse or exploitation", it said.
Abdi Farah Shirdon, the prime minister, said in a statement that the government was "deeply troubled by the alleged rape ... involving a number of personnel from AMISOM".
"The Somali government will not tolerate violation of human rights, in particular sexual violence ... perpetrators will be dealt with to the fullest extent of the law," Shirdon warned.
AU troops, including soldiers from five nations - Burundi, Djibouti, Kenya, Sierra Leone and Uganda - have been battling al-Qaeda-linked al-Shabab fighters in Somalia since 2007.
The attack allegedly took place in an AMISOM army base in the Maslah district of Mogadishu, Shirdon said, an area on the city's outskirts wrested from al-Shabab fighters by Ugandan troops last year.
If confirmed, the case - which has been widely reported in recent days by media in Mogadishu - will badly dent the reputation of the AU force, and play into the hands of al-Shabab.
Somalia's army, an often ragtag force with militia fighters, has been in the past accused by rights groups of a string of abuses against women, including rape.
Still, the extreme nature of the woman's allegations and the accusations of AMISOM involvement have shocked many.
In March, Human Rights Watch (HRW), the US-based rights monitor, detailed the "enormous problem" of the rape and sexual abuse of women and girls in Mogadishu, including by government soldiers and militia fighters.
HRW disclosed that many of those attacked are too frightened of reprisals to tell the authorities, while even reporting on rape in Mogadishu carries its own risks.
A Somali journalist and a rape victim he interviewed were both sentenced to a year in prison in February, but they were released after two months in jail after the case sparked widespread international criticism.