Rebel soldiers arrested Mali’s President Ibrahim Boubacar Keita and Prime Minister Boubou Cisse on Tuesday afternoon following weeks of political tension in the country.
The dramatic move followed the seizure of an army base near the capital Bamako that morning.
In a statement, the Economic Community for West African States said that its members would close land and air borders to Mali and pledged to demand sanctions against “all the putschists and their partners and collaborators”.
The 15-nation bloc — which includes Mali — also said that it would suspend the country from its internal decision-making bodies.
“ECOWAS has noted with great concern the seizure of power by Malian military putschists,” said the statement, which was originally published in French.
Mali has been in the grip of a deep political impasse since June, with President Keita facing increasingly strident demands for his resignation.
The opposition June 5 Movement, named for the date of its first protest, has been channelling deep anger over a dire economy, perceived government corruption and a brutal jihadist conflict.
The opposition alliance’s anti-Keita campaign veered into crisis last month when at least 11 people were killed over three days of unrest that followed a protest.
In an effort to avoid chaos in notoriously unstable Mali, ECOWAS then stepped in to mediate.
The bloc suggested the formation of a unity government and other measures late last month, but stuck by Keita.
But the June 5 Movement has repeatedly spurned compromise proposals, and has continued to demand Keita’s departure.
The political opposition declared a new phase of anti-government rallies on Monday.
Keita, 75, is currently being held by rebel soldiers outside of the capital.