Thirty-six civilians were killed in Burkina Faso in what government called a terrorist attack on a market in Sanmatenga province.
Armed militants forced their way into the market of Alamou and attacked people there before burning the building, government said in a statement.
The bloodshed is part of a surge in violence in the West African country that killed hundreds, forced nearly a million from their homes and made much of the north ungovernable over the past two years.
“Repeated attacks on innocent civilians call for real co-operation between defence and security forces,” government said.
President Roch Marc Kabore called for two days of national mourning in response. It was not immediately clear who was responsible.
Islamist groups with links to al Qaeda and Islamic State carried out increasingly brazen attacks against civilian and military targets in Burkina Faso in recent months, including an attack on a mining convoy in November that killed nearly 40 people.
The country was once a pocket of relative calm in the Sahel region, but its home-grown insurgency was amplified by a spill-over of jihadist violence and criminality from northern neighbour Mali.