Bamako, Mali - Mali's military government says Islamist militants have massacred 132 civilians in the central Mopti region, in one of the deadliest attacks of the decade-long militant insurgency.

Mali has declared three days of mourning after gunmen suspected to be Islamist militants killed 132 villagers in the central Mopti region.

The attack on three villages the evening of June 18 is one of the deadliest since Mali's conflict began in 2012.

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A government statement was read on state TV ORTM Monday night by presenter Mariam Kone.

She says the government condemns with the utmost rigor the attacks and abuses perpetrated against peaceful populations. Kone says the government reassures that all measures will be taken to find and bring the perpetrators of these criminal acts before the court.

The attack in Mopti is the latest in a wave of attacks on civilians in Mali and neighboring Burkina Faso.

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Last week in Burkina Faso, militants killed 86 civilians in an attack in the northern Seytenga area.

The U.N. mission to Mali, known as MINUSMA, in a statement Monday night condemned the attacks in central Mali.

The statement noted recent attacks also took place in several areas of Gao region, causing the deaths of dozens of civilians.

Local officials told AFP this week that 24 civilians were killed in Ebak, Mali, 35 kilometers north of the regional capital.

A local political movement reported that Islamist militants killed 22 men in Izingaz in Menaka region on June 12.

Mali's military government has not commented on the growing insecurity and violence in the country's northern regions.

The rise in violence comes as the French military is in the process of withdrawing from the region over Mali's working with Russian mercenaries.

Human Rights Watch and news reports quote locals saying Mali's army and Russian mercenaries killed hundreds of civilians in Moura, in central Mali, in March.

The military denies killing any civilians, says there are only Russian "instructors" in Mali, and says the Moura attack killed more than 200 Islamist militants.