It was the worst outbreak of violence since a failed coup in May.
The United Nations Security Council is ready "to consider additional measures" against powerbrokers in Burundi following deadly coordinated pre-dawn assaults on three army bases in the country on Friday, while urging calm and dialogue.
The council's 15 member countries "condemned in the strongest terms the recent attacks by unidentified assailants and urged all involved actors to refrain from violence," US Ambassador Samantha Power said following closed-door talks.
France — one of the five permanent members of the UN Security Council — had on November 10 proposed a draft resolution that threatened targeted sanctions against Burundi political leaders who are fuelling violence or thwarting efforts to end the crisis through dialogue.
It was the worst outbreak of violence since a failed coup in May, sparked by President Pierre Nkurunziza's bid for a third term in office, which he later won in disputed elections in July.
Burundi's army said 12 gunmen were killed and another 21 captured following the series of coordinated early morning assaults on the Ngagara base and a military training college, both in the capital Bujumbura, as well as on a base in Mujejuru, 25 miles (40 kilometers) away.
Power appealed for immediate talks to prevent more bloodshed.