The Congolese government has arrested Thomas Lubanga, the leader of the Union des patriotes Congolais (UPC), a key political movement in the northeastern district of Ituri, a government official announced on Tuesday.
"Lubanga is in the central penitentiary in Kinshasa and from now on the matter is in the hands of the judicial authorities," Henri Mova Sakanyi, the spokesman of the Democratic Republic of Congo (DRC) government, said.
Lubanga, whose faction of the UPC - a former militia group - is accused of widespread human rights abuses, was arrested on Saturday in Kinshasa, the nation's capital.
"We are surprised that our leader has been taken. We demand that he be freed immediately and unconditionally," Faustin Uma Unen, Lubanga's political adviser, said.
Other militia leaders from Ituri were arrested earlier in March and placed in the same prison. They include Floribert Ndjabu Ngabu, leader of the Front des nationalistes et integrationniste [FNI], and his aides, Goda Sukpa and Germain Katanga, who were recently promoted to generals in the national army.
The arrests follow the killing on 25 February of nine Bangladeshi soldiers from the UN peacekeeping mission known as MONUC in Kafe a village, an FNI stronghold, 60 km northeast of Bunia - the main town in Ituri. A week after the death of the Bangladeshis, MONUC troops stormed an FNI stronghold nearby, killing at least 60 militiamen.
Both the FNI and the UPC, which are political rivals, have denied involvement in killing the peacekeepers and accuse each other of responsibility.
Members of the FNI are mostly from the Lendu ethnic group while those in the UPC are mostly Hema. Since 1999, tens of thousands of people have been killed and others displaced in the area that is rich in diamonds, gold and other natural resources.