Attackers dressed as traditional Dogon hunters targeted Fulani herders in the villages of Ogossagou and Welingara in Mopti region, officials say.
More than 130 people were killed in an attack on a Fulani village in central Mali on Saturday, the United Nations said, as a delegation visited the country.
Survivors accused traditional Dogon hunters of carrying out the deadly raid in Ogossagou, according to Boubacar Kane, the governor of Bankass district which covers the village. A security source told AFP the victims were shot or hacked to death with machetes.
"The Secretary-General is shocked and outraged by reports that at least 134 civilians, including women and children, have been killed," Antonio Guterres's spokesman said in a statement, adding he called on Malian authorities "to swiftly investigate it and bring the perpetrators to justice".
The attack was launched at dawn on Saturday in the village near the border with Burkina Faso, said several sources. The district has been the scene of frequent inter-communal violence.
Two witnesses questioned separately by AFP said hunters had burned down nearly all the huts in the village.
Guterres's spokesman said the UN mission in Mali, MINUSMA, provided air support to deter further attacks and assisted with the evacuation of the injured.
The massacre took place as a delegation from the United Nations Security Council visited the Sahel region to assess the militant threat there.
Earlier the UN said the visiting ambassadors from the Security Council countries met on Saturday with Mali's Prime Minister Soumeylou Boubeye Maiga and discussed with him the volatile situation in the centre of the country.
While local attacks are fuelled by accusations of grazing cattle on Dogon land and disputes over access to land and water, the area is also troubled by militant influence.
In the past four years, militants have emerged as a threat in central Mali. A group led by radical Islamist preacher Amadou Koufa has recruited mainly from the Muslim Fulani community.
Since then, there have been repeated clashes between the nomadic Fulani herders and the Dogon ethnic group.
Last year that violence cost the lives of 500 civilians, according to UN figures.
In January, Dogon hunters were blamed for the killing of 37 people in another Fulani village, Koulogon, in the same region.
The Fulani have repeatedly called for more protection from the authorities.
The government in Bamako has denied their accusations it turns a blind eye to - or even encourages - Dogon attacks on the Fulani.
Once considered a beacon of democracy and stability in Africa, Mali in recent years has been dogged by a coup, civil war and Islamist terrorism.
Al Qaeda-linked militants took control of the desert north in early 2012, but were largely driven out in a French-led military operation launched in January 2013.
In June 2015, Mali's government signed a peace agreement with some armed groups, but the militants remain active, and large tracts of the country remain lawless.
Despite the presence of UN peacekeepers, a strong French military contingent and the creation of a five-nation military force in the region, militant violence has not abated.