Guinea-Bissau's government has said that its security forces executed a police officer earlier this week as he turned himself in over his role in what the regime describes as a coup bid.

Jaime Jose Nhate, chief of staff for the interior ministry, said late Thursday that civil society organisations had informed the minister of Major Yaya Dabo's intent to turn himself in.

"Measures were taken to guarantee Dabo's safety. Two unarmed security agents were even sent to ensure the security" of the vehicle which drove Dabo to the police station.

"Security agents learned that he (Dabo) was responsible for the shooting of one of their comrades" the night before, as police, soldiers and paramilitary police combed the capital for suspects.

As he arrived at the police station "officers on duty encircled his vehicle. He was shot at and killed."

On December 26, troops overran the armed forces headquarters in the troubled west African country's capital in what the authorities later described as a failed coup attempt led by the navy chief, who is now under arrest.

Deadly clashes erupted the following night as loyalist forces hunted suspected coup plotters.

Dabo was the brother of former territorial administration minister Baciro Dabo, who was killed in 2009 three months after the assassination of his close ally, President Joao Bernardo Vieira.

Baciro Dabo was also seen as a strong contender in presidential elections following Vieira's death in an apparent revenge attack by soldiers angered by the killing of their army chief.

The poor former Portuguese colony is notoriously unstable, with a history of coups and army mutinies. Today it has become a transit point for drug cartels who use it as a hub to traffic drugs to Europe.

Only six hours by plane from South America with an un-policed coastline and scores of uninhabited islands, the small country with weak government institutions has become a major channel for South American cocaine.

According to the UN drug agency UNODCY, over 40 tonnes of cocaine passed through the country of 36,000 square kilometres between 2007 and 2009.

Last year, the US Treasury Department froze the assets of navy chief Jose Americo Bubo Na Tchuto -- now under arrest for his role in the alleged coup plot -- and airforce head Ibraima Papa Camara for their "significant role" in drug trafficking.

During the press conference Interior Minister Fernando Gomes said calm had returned to Guinea Bissau and "the situation is under control."

Military spokesman Vilela Carlos said the search for suspects was still under way.

"Many suspects are on the run. So, to be reassured, we need to arrest all of them. We are working day and night and we have deployed our agents on the ground," said Carlos.

On Thursday 25 troops arrested for their role in the alleged coup plot, including navy chief Bubo Na Tchuto, were paraded in front of journalists.