Dozens of people in eastern Congo were confirmed dead on Sunday after gun- and machete-wielding militants from the Uganda-based rebel group ADF launched an attack at the southern edge of the city of Beni.
The governor of the North Kivu province said approximately 36 people had died, while Teddy Kataliko, the head of non-governmental organization Civil Society of Beni, put the death toll at a minimum of 40.
The attack, launched late Saturday, is the rebel group's deadliest this year.
The Congolese government has declared three days of national mourning following the attack, spokesman Lambert Mende said.
The attack comes days after a meeting between the President of Congo, Joseph Kabila, and the President of Uganda, Yoweri Museveni, about efforts to better coordinate military response to rebel attacks.
A local from Beni's Rwangoma neighbourhood said people in the area had assumed the uniformed rebels were soldiers and only fled once they began attacking.
The Islamist ADF was founded in Uganda in 1995 and later moved to Congo. Beni is located just 50 kilometres west of the Ugandan border.
Dozens of armed groups seeking control over territory and mineral resources have remained active in eastern Congo since the 1996-2003 Congo wars.