The two, who were reportedly just teenagers, were killed by firing squad on Wednesday in front of hundreds of residents in the town, according to media reports.
“The public summary execution of these two young women, with no recourse for legal defense protection, is a horrific act which demonstrates the extremists’ complete disregard for human life, particularly of the vulnerable,” Augustine Mahiga, the Secretary-General’s Special Representative, said in a statement.
He added that those responsible for this “appalling” crime should be held accountable.
The country – which has not had a functioning central government since 1991 – has been torn apart by decades of conflict and factional strife, more recently with al-Shabaab and other groups fighting the Transitional Federal Government.