Prolonged, heavy gunfire around the Government Palace in Guinea-Bissau's capital has signaled a coup attempt in this West African country with a long history of military takeovers.

The state broadcaster has reported that the shooting has damaged the government building and that "invaders" are holding officials.

President Umaro Cissoko Embalo, a former army general, was believed to be inside the building at the time of the attack.

The 15-nation West African regional bloc known as ECOWAS, already grappling with three other coups in member states over the last 18 months, called Tuesday's violence a coup attempt and said it is following the situation in Bissau "with great concern."

"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," the statement said in a tweet.

In Portugal, the former colonial ruler of the country, the Foreign Ministry said in a tweet: "We strongly condemn the attack on the government palace in Bissau and appeal for the immediate end of this violent action against the president and government of Guinea-Bissau. Constitutional order must be respected by all."

Portuguese Foreign Minister Augusto Santos Silva condemned what he said was "armed activity" in Bissau.

"There is armed activity in Bissau directed at the legitimate authorities of Guinea-Bissau, its president and government," Santos Silva told Portugal’s Lusa news agency.

Embalo was declared the winner of the December 2019 runoff vote, though the results were contested by his opponent, Domingos Simoes Pereira. Embalo then started forming 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 experienced four coup d’etats and more than a dozen attempted coups.

The small nation of around 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 seen 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 have yet to organize new elections.