Armed men killed 37 Fulani civilians on Tuesday in central Mali, where ethnic violence cost hundreds of lives last year, the government said.
Violence between Fulani and rival communities has compounded an already dire security situation in Mali's semi-arid and desert regions, which are used as a base by jihadist groups with ties to al Qaeda and Islamic State.
The government said in a statement that the attackers, who were dressed as traditional Donzo hunters, raided the village of Koulogon in the central Mopti region and that some of the victims were children.
Moulage Guindo, the mayor of Bankass, the nearest town, said the attack occurred around the time of the first call to prayer of the new year and targeted the Fulani part of Koulogon.
He said another part of Koulogon is mostly inhabited by Dogon, an ethnic group to which the Donzos are linked, less than 1km away.
Mali has been in turmoil since Tuareg rebels and loosely allied Islamists took over its north in 2012, prompting French forces to intervene to push them back the following year.
Islamists have since regained a foothold in the north and centre, tapping into ethnic rivalries to recruit new members.