Earlier on Tuesday, gunfire was heard near the Government Palace in Bissau, where President Umaro Sissoco Embalo and Prime Minister Nuno Gomes Nabiam were holding an extraordinary meeting of the Council of Ministers.
According to Lusa Agency, soldiers entered the building and ordered the ministers to leave.
"The latest information I have is positive given that the president is already at his palace, at his official residence ... but we still don't know if the attack is over," Portuguese Foreign Affairs Minister Augusto Santos Silva told Portuguese broadcaster RTP in an interview on Tuesday afternoon.
A post on Embalo's Facebook account on Tuesday evening said "calm returns to Bissau!" and showed photos of him meeting with military officers, including Gen. Biague Na Ntan, Chief of the General Staff of the Revolutionary Armed Forces of the People (FARP), the Bissau-Guinean military.
Another post on an unverified Twitter account claiming to be Embalo said the situation was "under government control."
In an interview given to Jeune Afrique news agency, Embalo said he was still in the presidential palace and that there were "many dead" after the shooting in the capital, which lasted for more than five hours. He said the deaths were the work of "isolated elements."
He added they had begun arresting some of those involved.
Gunmen have been reported in the city's streets, with video footage posted online showing men holding recoilless antitank rifles and machine guns outside the Government Palace.
No statement has been made so far by the gunmen about who they are or what their motives or goals are.
A former Portuguese colony that fought a long liberation war, Guinea-Bissau gained independence in 1974 following the overthrow of the Estado Novo government in Lisbon by the leftist Carnation Revolution. However, since then it has suffered four coups d'etat, the most recent of which happened in 2012.
Embalo, a former general took office in 2020 following victory in elections that were disputed by the African Party for the Independence of Guinea and Cape Verde (PAIGC), the liberation front that led the country to independence and has been the dominant party ever since. His party, Madem-G15, also called the Movement for Democratic Alternation, is composed largely of disaffected PAIGC members who left the party in 2018.
Embalo has compared himself to Philippine President Rodrigo Duterte, attempting to cultivate a larger-than-life personality and pushing a populist ideology he calls "Embaloism." He has described Embalosim as "order, discipline and development."
The coup attempt is the fourth in an ECOWAS country in less than a year, following a military coup in Mali in May 2021, one in the Republic of Guinea in September 2021, and third in Burkina Faso last month.