Kenyan activists and Burundian expatriates hold placards and candles during a candlelight vigil held for Burundi in Nairobi on Dec. 13. (Dai Kurokawa/European Pressphoto Agency)

— The U.S. State Department has warned American citizens to depart Burundi after a recent surge in violence left nearly 100 people dead in a single day.

On Friday, 87 people were killed — 79 attackers and eight soldiers — when gunmen raided three military sites in and around the capital, Bujumbura, according to Burundi’s government.

The small East African country has been embroiled in a mounting conflict since April, when President Pierre Nkurunziza defied constitutionally mandated term limits and announced that he would run for a third term. A failed coup in May prompted a brutal government crackdown, and Nkurunziza won the July presidential election. Now the military is fighting a persistent armed opposition that appears to have stepped up its efforts.

Friday marked one of the most brazen and organized attempts by the opposition to target government institutions. But some Burundians claimed that the military’s response was aimed at more than just quelling the attack. Witnesses said civilians were taken from their homes and shot at close range, according to the Associated Press, in what appears to be part of a string of extrajudicial killings.

“The US Department of State warns US citizens against all travel to Burundi and recommends that US citizens currently in Burundi depart as soon as it is feasible to do so,” the department said in a statement Sunday.

Samantha Power, the U.S. ambassador to the United Nations, said the U.N. Security Council was ready to consider “further steps.”

“The members of the Security Council demand that all armed groups put aside their arms and cease all forms of destabilizing activities in order to end the cycle of violence and retaliation,” she said at a news conference Friday.

At least 300 Burundians have been killed and more than 200,000 have fled the country since the conflict erupted, according to the United Nations. Many are worried that it could take on a more ethnic component, pitting Hutus and Tutsis — the same groups involved in the 1994 Rwandan genocide — against each other. During Burundi’s 12-year civil war, which ended in 2005, Nkurunziza led a Hutu rebel group against an army then led by the Tutsi minority.

In October, President Obama removed Burundi from a trade preference program, writing in a letter to Congress that Nkurunziza has used “assassinations, extra-judicial killings, arbitrary arrests and torture” to crack down on the opposition.