Armed men killed at least 100 civilians in a rural district of northern Burkina Faso over the weekend, a local and a security source said on Monday.
The attackers struck on Saturday night in Seytenga commune, part of Seno province, which lies in borderlands where militants linked to al Qaeda and Islamic State are waging an insurgency.
One security source told Reuters at least 100 people were killed.
A local source who did not wish to be named said the provisional death toll stood at 165.
The United Nations condemned the attack that "claimed many victims" in a statement on Monday and called on authorities to bring perpetrators to justice.
The government is expected to provide a death toll later on Monday.
Armed men killed 11 military police in the same area last Thursday.
The highest death toll since the start of Burkina Faso's security crisis was from an attack last June when militants killed over 130 civilians in a northeastern village.
Violence linked to Islamist insurgents has killed thousands and displaced millions across Burkina Faso and neighboring Mali and Niger since 2015.
Army officers angry about the escalating attacks overthrew Burkina Faso's president in January and vowed to improve security, but levels of violence have remained high.
The military government has cited security concerns for its decision to take 36 months to restore democratic rule, despite pressure from West Africa's regional bloc ECOWAS to hold elections sooner.
Almost 1.7 million people in Burkina Faso, Mali, Niger and Chad are expected to face emergency levels of food insecurity in the coming months - a situation exacerbated by the violence, crushing poverty and record-high food prices, the United Nations' aid agency said in May.