Burundi on Wednesday expelled a World Health Organisation (WHO) representative and three senior health experts.
Dr Walter Kazadi Mulombo - who was the WHO boss in Bujumbura - and his three colleagues were declared persona non grata and given up to May 15 to leave the country.
The others are Prof Daniel Tarzy, Dr Ruhna Mirindi Bisimwa and Dr jean-Pierre Mulunda Nkata.
The Foreign Ministry wrote a note verbale to the WHO Africa head offices in Brazzaville, asking that the four officials leave the country, but did not specify the reasons.
Burundi had by Wednesday reported 15 cases of Covid-19, with one death.
The country closed its main airport to international flights. But it has attracted public criticism for going on with planned elections due May 20 by allowing public rallies and gatherings.
Officials in Bujumbura said they will not permit election observers into the country unless they accept to take 14 days of quarantine. That would mean that they will come out days after ballots are cast.
Reports had earlier indicated WHO had raised questions on the testing procedures employed in Bujumbura. But the expulsion did not refer to any tiff with WHO.
President Pierre Nkurunziza is stepping down after three terms in office.