Armed men from Congo burst into a pub in the central African nation of Burundi and killed 36 people, an official said on Monday. One wounded man said an attacker yelled: “Make sure there’s no survivors.”

Burundi, a tiny nation still reeling from a civil war that killed more than 250,000 people, is awash in weapons but attacks like the one on Sunday night are rare. Still, the region borders eastern Congo, which is wracked by violence from a myriad of rebel groups.

Bujumbura province Governor Jacques Minani said the attackers targeted the pub in Gatumba, west of Burundi’s capital, after crossing the river from Congo.

Survivor Jackson Kabura, who was shot in the stomach, said the men entered wearing fatigues.

“I saw a man in military fatigues,” he said. “One of them said, ‘kill them all, kill them all. Make sure there’s no survivors’.”

President Pierre Nkurunziza has declared three days of mourning and gave the government one month to find the culprits.

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