At least 10 officers from Burundi's army and police force have reportedly fled the country since the beginning of this month amid ongoing repression in the country.
The group includes several senior officers.
Burundian security expert Gratien Rukindikiza put the total number of deserters at 13 and said they had fled owing to fears of repression because of their ethnicity or for being perceived as supporters of the country's political opposition.
Human rights activists say the Hutu-dominated government of President Pierre Nkurunziza is increasingly repressing ethnic Tutsis.
Burundi has been in turmoil since Nkurunziza announced last year that he would seek a third term in office despite a constitutional two-term limit. His election victory in July 2015 unleashed a wave of political violence in which hundreds have been killed.
In May, a court handed life sentences to 21 people, including senior military officers, who had been implicated in a failed coup attempt against Nkurunziza. Dozens of soldiers have been arrested on charges of supporting the opposition, Rukindikiza, the security expert, said.
Many of the detainees belong to the minority Tutsi ethnic group.
Burundian army spokesman Gaspard Baratuza denied that the deserters had fled owing to ethnic repression or security fears, and said they were being manipulated by the opposition.
Their departure follows that of Colonel Adolphe Manirakiza, a former spokesman for the UN peacekeeping mission in the Central African Republic, who fled Burundi in April.