UN Secretary-General Ban Ki-moon voiced outrage on Wednesday after Burkina Faso's presidential guard detained the country's interim president and prime minister, and demanded their immediate release, AFP reports.
"This incident is a flagrant violation of Burkina Faso's constitution and transitional charter," Ban said in a statement.
Security forces linked to ex-leader Blaise Compaore burst into a cabinet meeting room and seized President Michel Kafando and Prime Minister Isaac Zida as well as two ministers, the parliament speaker said in a statement sent to AFP.
Ban said he was "outraged," a UN statement said.
UN envoy for west Africa Mohamed Ibn Chambas was in the capital Ouagadougou, holding talks with African governments to press for a return to the transitional regime.
Compaore was toppled in October 2014 and fled into exile in Ivory Coast after a popular uprising triggered by his attempt to extend his 27-year rule.
The transitional government has been charged with running the poverty-striken Sahel nation country until presidential and legislative elections are held, the first round of which is to take place on October 11.