Pictured here, slippers outside a communal space at a camp for displaced persons. Photo courtesy UNICEF
Armed men carried out the attack in the village of Barsalogho in north-central Burkina Faso on Saturday, killing dozens of civilians and security personnel and wounding others, local sources said.
A group linked to Al-Qaeda known by its Arabic initials JNIM, one of several rebel groups active in the troubled Sahel nation since 2015, claimed responsibility.
The EU "condemns in the strongest terms the terrorist attack" in Barsalogho, which "left hundreds of victims, mainly civilians", Borrell said in a statement.
The bloc "expresses its solidarity with Burkina Faso and conveys its condolences to the families of the victims and its wishes for a swift recovery to the wounded", he added.
The insurgency waged by rebels affiliated with Al-Qaeda and the Islamic State has also rocked neighbouring Mali and Niger, killing thousands and displacing millions across the region.
Borrell said the EU expressed its "strong concern amid the worsening security situation in the country and the sub-region" and encouraged efforts to avoid an escalation of violence.
UN chief Antonio Guterres also "strongly condemned the terrorist attacks", his spokesman Stephane Dujarric said on Tuesday.
The military-led Burkinabe authorities have not provided a toll and have stopped announcing civilian and military casualties in jihadist attacks for about a year.
But a group representing victims' families reported "at least 400 dead". One of its members told AFP they helped bury victims in mass graves that contained "more than 100 bodies".
A survivor, speaking on condition of anonymity, said she lost her husband and a brother-in-law and that "we haven't finished burying the bodies".
The UN humanitarian coordinator in Burkina Faso, Carol Flore-Smereczniak, said two humanitarian workers were among those killed.
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