Gunmen in Burundi launched coordinated attacks on three military bases in the capital Friday, sparking gun battles that left at least 12 of the attackers dead.
A Burundian army spokesman, Colonel Gaspard Baratuza, said in a statement that 21 attackers were captured along with some arms and explosives.
He said five soldiers were wounded. However, army soldiers, speaking on condition of anonymity, said that at least three soldiers were killed.
U.N. Secretary General Ban Ki-moon said the violence risked "a further destabilization of the situation in Burundi." Ban urged the "leadership of these groups and the national authorities to refrain from any further escalation of violence," according to his spokesman, and warned that "anyone responsible for ordering or committing human rights violations will be held individually accountable."
U.S. Ambassador to the U.N. Samantha Power said "high-level political dialogue" needs to begin immediately between the government and the opposition "to defuse the situation" or else risk the situation "evolving into mass violence."
The gunmen attacked the military sites in Bujumbura around 4 a.m. local time Friday.
Presidential media adviser Willy Nyamitwe wrote on Twitter that the strikes were a "diversion" by the attackers to try to free prisoners at the military camps.
He later wrote that the situation in the capital was returning to normal and the government has not declared a state of emergency.
Burundi has been plagued with unrest since April when the president announced he would seek a third term. Critics said he was violating the constitution's two-term limit as well as an agreement that ended Burundi's 12-year civil war.
The United Nations says violence since then has killed more than 240 people and prompted more than 200,000 Burundians to flee the country. The president was re-elected in July in a vote boycotted by the opposition.
The U.S. embassy in Burundi on Friday ordered its personnel to shelter in place and advised Americans in Bujumbura to take similar precautions.
In a statement earlier this week, U.S. National Security Council spokesman Ned Price called for all sides in Burundi to reject violence and take part in an internationally mediated dialogue, outside the country, to resolve the crisis.
He said the United States may impose sanctions on others who block peace efforts or resort to violence.