A helicopter operated by the peacekeeping force MONUSCO came under fire on Sunday after taking off from the city of Beni. A South African peacekeeper was killed and another one wounded.
Neither South Africa nor MONUSCO said who might be responsible, nor what kind of weapon was used to target the helicopter or what caused the casualties.
The Kinshasa government blamed the M23 in a statement on Monday. The group, which launched a major offensive last year, denied the accusation.
With around 18,200 personnel, MONUSCO has been deployed in eastern Congo since taking over from a previous U.N. operation in 2010. Its mandate includes supporting the DRC government's effort to stabilize the region.
But it has been the target of several sometimes violent protests against insecurity that have broken out in and around Goma over the past year.
Demonstrators accuse MONUSCO and a regional force set up in April last year of not doing enough to protect civilians and end bloodshed.
Hundreds took to the streets again on Monday, denouncing M23 advances which threaten Goma, despite a deal brokered in November under which the rebels agreed to a truce and to withdraw from recently seized territory.
