Gunmen killed about 15 people in an attack on a mosque in northern Burkina Faso during prayers on Friday, a security source and a local official told Reuters.
Gunmen entered the mosque in Salmossi in the Oudalan region bordering Mali and opened fire, the sources said. Other people were seriously wounded, the security source said.
The identities of the gunmen were not yet clear.
An Islamist insurgency by groups with links to Islamic State and al Qaeda crossed into Burkina Faso this year from Mali, igniting ethnic and religious tensions, especially in northern regions.
The attacks shattered a relative calm in Burkina which, until this year, was largely spared the violence which made large areas of the Sahel ungovernable.
The number of people forced to flee their homes in the worst-hit areas increased more than six fold since January to around 500 000, according to the United Nations and aid groups.
Last week, 20 people were killed in an attack by suspected jihadists on a gold mine in the north.