Seven children and four women were among 14 civilians, killed when a roadside bomb blew up their bus in northwestern Burkina Faso, the government said.
"The provisional toll is 14 dead," a statement said, adding that 19 more people were hurt, three of them seriously in Saturday's blast.
The explosion happened in Sourou province near the Mali border as students returned to school after the Christmas holidays, a security source said.
"The vehicle hit a homemade bomb on the Toeni-Tougan road," the source told AFP.
"The government strongly condemns this cowardly and barbaric act," the statement said.
No one claimed responsibility for the attack but jihadist violence in Burkina Faso has been blamed on combatants linked to both Al-Qaeda and Islamic State groups.
Meanwhile, the army reported an assault against gendarmes at Inata in the north on Friday, saying "a dozen terrorists were neutralised".
The deaths came the week after 35 people, most of them women, died in an attack on the northern city of Arbinda and seven Burkinabe troops were killed in a raid on their army base nearby.
Burkina Faso, bordering Mali and Niger, has seen frequent jihadist attacks which have left hundreds of people dead since the start of 2015 when Islamist extremist violence began to spread across the Sahel region.
In a televised address on Tuesday President Roch Marc Christian Kabore insisted that "victory" against "terrorism" was assured.
The entire Sahel region is fighting a jihadist insurgency with help from Western countries, but has not managed to stem the bloodshed.
Five Sahel states -- Burkina Faso, Mali, Mauritania, Niger and Chad -- have joined forces to combat terrorism in the fragile region that lies between the Sahara and the Atlantic.
Increasingly deadly Islamist attacks in Burkina have killed more than 750 people since 2015, according to an AFP count, and forced 560,000 people from their homes, UN figures show.