Heavy gunfire erupted on Tuesday near the Government Palace in Guinea-Bissau’s capital, witnesses said.
The reports raised fears of a coup attempt in the West African country, which has a long history of military takeovers.
Guinea-Bissau’s state broadcaster reported that the shooting had damaged the government building and that “invaders” were holding officials.
President Umaro Sissoco Embalo, a former army general, was believed to be inside the premises at the time of the attack.
Ecowas called Tuesday’s violence a coup attempt and said it is following the situation in Bissau “with great concern”.
The 15-nation West African regional bloc is already grappling with coups in three other member states in the past 18 months.
“Ecowas condemns this coup attempt and holds the military responsible for the bodily integrity of President Umaro Sissoco Embalo and the members of his government,” its statement said.
Mr Embalo was declared the winner of the December 2019 run-off vote, though the results were contested by his opponent, Domingos Simoes Pereira.
Mr Embalo then started to form a new government with support from the military while a Supreme Court election challenge was still pending.
Since gaining independence from Portugal in 1974, Guinea-Bissau has faced four coups and more than a dozen attempts.
The small nation of about 1.5 million people has long been beset by corruption and drug trafficking. In the 2000s, it became known as a transit point for cocaine between Latin America and Europe as traffickers profited from corruption and weak law enforcement.
West Africa has been shaken by a spate of coups since August 2020, with military juntas grabbing power in Mali, Guinea and Burkina Faso. Despite international pressure for a return to constitutional rule, none of the military rulers has organised new elections.
The African Union said it was very concerned about what it described as an attempted coup in Guinea-Bissau and called on the military to free detained government members.
“The President of the African Union Commission, Moussa Faki Mahamat, is following with grave concern the situation in Guinea-Bissau, consisting of an attempted coup against the country’s government,” the AU said.
“He calls on the military to return to their barracks without delay and to protect the physical safety of President Umaro Sissoco Embalo and members of his government and to immediately free those of them who are in detention.”
