U.S. Secretary of State John Kerry is urging all parties in Burundi to stop violence and instead begin dialogue to end what has been months of unrest in the country.
Kerry wrote on Twitter Sunday that the killing must end, including "disproportionate response by security services."
Earlier in the day, the State Department told U.S. citizens to avoid traveling to Burundi, and recommended that those already in the country leave as soon as possible as political violence persists.
More than 80 people were killed Friday when armed attackers raided army facilities in the capital, Bujumbura. Among the dead were eight security officers and scores of assailants, according to an army spokesman.
The unrest began in 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.
Washington-based humanitarian group Refugees International said Monday it is concerned about claims from Burundian refugees in Rwanda who said they have been recruited by armed groups in Burundi.
Rwanda is hosting nearly one-third of the refugees, including 45,000 at its Mahama camp. Refugees International's report cites international officials who describe recruitment efforts at Mahama, mainly targeting adult men, but some cases involving children between the ages of 15 and 17. The report says those who decline to join the armed groups face harassment.
Refugees International is calling on Rwanda to ensure any recruitment is immediately stopped, and to publicly affirm that such efforts violate the country's law and international law. It also wants the United Nations and African Union to impose sanctions against anyone violating "the civilian and humanitarian character of asylum."