"I was released yesterday (Wednesday) and I am visiting certain friends," Rear Admiral Jose Americo Bubo Na Tchuto told AFP as he paraded through Bissau in a large black car, surrounded by bodyguards.

A military source, speaking on condition of anonymity, said the decision to release Na Tchuto, who has been linked to previous coup bids and was named a drug kingpin by the United States, was taken by army chief Antonio Indjai who successfully ousted government on April 12.

He was released with 18 co-accused in what political observers described as a dramatic turn of events.

"They were accused of wanting to overthrow Carlos Gomes Junior's government, which was then overthrown by the army (in April) so I see no reason to keep them in detention which would only have fueled hatred between our soldiers," said the military source.

Witnesses reported that Na Tchuto's home was closely garded by naval officers.

The former navy chief is one of several soldiers under European Union and US sanctions.

Na Tchuto was first accused of a coup attempt in 2008, and fled the country to Gambia.

He resurfaced in April 2010 during an army mutiny in which Indjai ousted army chief Jose Zamora Induta.

With Indjai now army chief, Na Tchuto was re-appointed as navy chief which drew swift condemnation from abroad.

The two men were close allies, but later fell out and Na Tchuto was arrested after a December 26, 2011 failed coup bid which saw clashes between troops in what some observers said was a settling of scores between the two men.

On April 12 Indjai led a coup against Gomes' regime, in the middle of an election process, and the country has since set up a transition government.

Constant power struggles between the army and state in the former Portuguese colony have led to chronic instability, coups, counter-coups and assassinations. This has allowed cocaine trafficking to Europe to flourish.

The deserters were all members of a former rebel movement, the National Congress for the Defence of the People (CNDP), who were integrated into the army early in 2009, following a peace pact.

They "left the ranks of the FARDC (Congolese army) yesterday (Wednesday)," Lieutenant-Colonel Vianney Kazarama, spokesman for the March 23 Movement (M23), told AFP.

Three lieutenant-colonels and four majors deserted from the Armed Forces of the Democratic Republic of Congo (FARDC) with troops under their command -- a total of 166 men -- and brought their arms and ammunition with them, Kazarama said.

With the exception of a lieutenant-colonel who came from Sud-Kivu province, all the senior officers were based in Nord-Kivu province, where the army has been fighting M23 forces. One of the majors was responsible for logistics and two others were in army intelligence, the M23 spokesman said.

A senior officer in the FARDC confirmed to AFP that "certain officers are in the process of deserting", without giving their numbers.

"I can't be surprised because they are ex-CNDP men who are going to join their brothers. It's not surprising that they are taking weapons because until their desertion they held command posts in the FARDC," he added.

The deserters all "responded to the call by Colonel (Sultani) Makenga", the leader of M23 and a former leader of the CNDP who deserted early in May and demanded the full implementation of the peace accords of March 23, 2009, which covered the integration of CNDP rebels into the army, Kazarama said.

Troops who were once in the CNDP have been deserting for weeks, blaming their poor conditions in the army, and the FARDC has attacked them in the Virunga National Park, near the border with Rwanda and Uganda.

In spite of frequent shelling by the army, the mutineers have held their positions on the Runyony, Mbuzi and Chanzu hills in the park.

In recent days, a relative calm has prevailed in the conflict, which has displaced 200,000 local villagers and turned more than 20,000 into refugees on the far side of the border, according to the United Nations.

People are still leaving the combat zone, UN sources said.

"The residents who fled the fighting in Runyony have come back, and others elsewhere are fleeing the threat and the mistreatment on the part of the FARDC," Kazarama said.