Martin Kobler, head of a DRC peacekeeping mission known by its French initials, MONUSCO, said a U.N. helicopter came under fire last week from members of the March 23 Movement in the eastern part of the country.
MONUSCO didn't indicate the extent of damage or if any casualties resulted. Kobler said the mission was determined to defend Congolese airspace despite the M23 assault.
U.N. peacekeepers in DRC are mandated to use force as they fight alongside the Congolese military in the eastern part of the country.
M23 is accused of committing war crimes in its campaign against the government. It took control over parts of eastern DRC briefly last year.
Robinson, a former Irish president, expressed "deep concern" about the incident in a Sunday statement.
She met with Kobler and regional delegates last month to press for a swift resolution to the conflict.
Fighting between M23 and government forces has displaced more than 100,000 people in the country since last year. Rwanda is accused of backing M23, an allegation it denies.
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