BENI, DR Congo, Aug. 15 (Xinhua) -- Democratic Republic of Congo (DR Congo) government has declared three days of national mourning starting Monday, following the massacre of 45 people in the eastern part of the country by suspected Ugandan rebels over the weekend.

Government Spokesman Lambert Mende, who made the announcement on the national broadcaster on Sunday evening, said flags across the entire national territory will fly at half mast during the mourning period.

"Following instructions from the president of the republic, the government hereby declares three days of national mourning starting Monday following the massacre of 45 people in Beni territory, North Kivu province, by suspected Allied Democratic Forces (ADF) rebels," Mende said.

The government noted that the massacre was a work of a radicalized or jihadist group.

"The terrorist massacre that occurred in the east of the country is not different from those which happen in Mali, Cameroon, Nigeria or Somalia, and even in Belgium, the U.S. and in France," DR Congo President Joseph Kabila said on Sunday in Goma, provincial capital of North Kivu.

"What happened in Beni is an Islamist threat of radical terrorists that is happening everywhere," he added.

North Kivu governor Julien Paluku urged the population to remain vigilant and support the DR Congo armed forces so that they can be able to defeat "the ADF terrorists."

At least 45 civilians were killed on Saturday night in Beni by suspected Ugandan rebels ADF.

The ADF rebels, who have been active in eastern DR Congo since 1994, are accused of having killed over 600 civilians since October 2014 in Beni town.

The Congolese army and the UN peacekeepers have in recent months launched operations against ADF, although the rebel group's threat level seems not to be declining.