The African Union said that three civilians were killed and two others injured during a firefight between its forces in Somalia and Islamists from the Al-Shabaab group.
The African Union Mission in Somalia (AMISOM) said its troops clashed with Al-Shabaab fighters who had laid a roadside ambush on Monday northeast of Janale in Lower Shabelle, a hotbed for the insurgents.
"Regrettably, three women were killed in the crossfire while two were injured and are currently receiving medical attention at the AMISOM hospital," AMISOM said in a statement late Tuesday.
"We would like to render our sincere apologies and heartfelt condolences to the families of the deceased and wish the injured a speedy recovery."
AMISOM head Ambassador Francisco Madeira said the incident was "unfortunate" and that its peacekeeping force deployed in Somalia "remain committed to protecting the population".
AMISOM troops, which support Somalia's ill-equipped national army in the fight against Al-Shabaab, have been accused of killing civilians during past operations.
US forces, which regularly target the Islamists with airstrikes, announced in April that one of its drone attacks the previous year resulted in two civilian deaths.
It was just the second time the US military admitted to civilian deaths from its drone programme in Somalia, though rights groups say the true figure is higher.
Al-Shabaab, an Al-Qaeda affiliate in the Horn of Africa, has fought for over a decade to topple the internationally-backed Somali government in Mogadishu.
In 2011, AMISOM forces pushed Al-Shabaab out of their holdouts in Mogadishu, and the insurgents have since lost much of the territory they once controlled.
But they still carry out regular attacks against civilian and government targets, inflicting mass casualties not just in Somalia, but elsewhere in the region.