At least 30 people, including nine soldiers, were killed in three separate incidents in Mali.
Twenty-one were killed when gunmen attacked a village in central Mali, burning houses, crops and livestock.
A group of eight soldiers also died in an ambush, while another was killed in an attack on a military camp in the Gao region.
Mali has been experiencing instability since 2012, when an Islamist rebellion broke out in the north.
The village of Ogossagou, where one of Friday's attacks took place, is mainly home to the Fulani, a largely Muslim ethnic group who have traditionally worked as herders.
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Other ethnic groups in Mali - including the Dogon community - accuse the Fulani of being linked to jihadist groups operating in the Sahel region.
These accusations have fueled inter-ethnic violence in recent years.
Last March, 160 people were killed in another attack in Ogossagou, alleged by the authorities to be a Dogon militia.
The attack led to several protests against perceived government inaction, and the Prime Minister of Mali at the time, Soumeylou Boubeye Maiga, later resigned.
No one claimed responsibility for the latest incident, but village chief Aly Ousmane Barry told local media that the gunmen struck several hours after the withdrawal of government troops from the area.
In another incident, Malian security forces said on Twitter that they had suffered "material damage" during an ambush in the village of Bintia, which killed eight soldiers.
A ninth soldier was killed in another attack on a Mondoro camp, regularly targeted by militants.
Since 2012, Malian forces have successfully regained control of large tracts of territory taken by militants with the help of France, which has 4,500 troops deployed in the region. The UN has 13,000 peacekeepers in Mali.
But thousands of lives have been lost as Mali struggles to contain the violence, which has spread to neighboring Burkina Faso and Niger.
The fight against militants in the Sahel region is seen as important for maintaining security further, including in Europe.
French Foreign Minister Florence Parly visited Washington last month hoping to persuade the United States to continue its logistical support - drones, intelligence and transportation - which she said was crucial to the French operation.