The African Union says it has suspended Burkina Faso and will impose sanctions on coup leaders if they do not restore the interim government and release its senior officials.
The AU statement, issued on Friday, followed a meeting of the Peace and Security Council in Addis Ababa, Ethiopia.
Soldiers from the elite presidential guard (RSP) stormed into a cabinet meeting on Wednesday and abducted President Michel Kafando and Isaac Zida, the prime minister, disrupting a transition period due to end with polls next month.
General Gilbert Diendere, a former spy chief and close ally of Blaise Compaore, the former long-term president, was named junta head the next day.
The AU gave coup leaders 96 hours, or until September 22, to restore the transitional government or face travel bans and asset freezes.
"Council decides to suspend, with immediate effect, the participation of Burkina Faso in all AU activities," the statement said, adding that members of the RSP linked to the kidnappings would be held legally accountable for their actions.
Burkina Faso, whose citizens toppled Compaore last year as he sought to extend his 27-year rule, had been seen as a model by pro-democracy campaigners across sub-Saharan Africa.
The coup has been condemned by the US, former colonial power France and the UN.
'Lack of dialogue'
For his part, Senegal's President Macky Sall deplored a "lack of dialogue" as mediators entered a second day of talks between the interim and coup leader.
"There is a critical lack of dialogue among actors, and this will negatively affect national unity and cohesion," Sall said in remarks late on Friday night after a full day of meetings in the capital, Ouagadougou.
Diendere, a former top Compaore aide, said he met some members of the international community and was "considering meeting the different political parties very soon".
But transition officials have insisted that the junta needs to leave.
"The mediators are here to help us find a compromise, but there are things that are non-negotiable," Jean Hobert Bazie, a transitional legislator, who joined others in calling for the return of Kafando.