The alleged mastermind of an attack on a military barracks in Guinea-Bissau, which government has described as a coup attempt backed by Portugal, will face a military court, the army said Tuesday.

"Captain (Pansau) N'Tchama will appear in front of a military court which will be open to the public and naturally, the press. All necessary conditions for a fair judgement will be guaranteed," said military spokesman Colonel Daba Na Walna.

N'Tchama was due to address the media on Tuesday to tackle the accusations against him, but his appearance was cancelled.

"We convinced (army chief of staff General Antonio) Indjai that a judgement such as that against Pansau is not made in the public arena. He understood and adjourned the press conference," Na Walna told journalists.

Captain N'Tchama was arrested on Saturday morning in Bolama, capital of the Bijagos arpichelago and situated on the island of the same name. He had been tracked by a unit of 158 men.

The Sunday dawn attack on an elite "Red Beret" army barracks left at least seven people dead, including six of the attackers.

Transition authorities in the west African nation have accused former colonial ruler Portugal of instigating the attack in a bid to re-instate former prime minister Carlos Gomes Junior who was ousted in an April 12 coup.

A transition government has since taken over after the putsch which interrupted a presidential election between the first and second rounds, which Gomes was leading after the initial vote.

N'Tchama was the head of a commando unit that is believed to have assassinated president Joao Bernardo Vieira in 2009. He returned last week from Portugal where he had been undergoing military training since July 2009, security sources said this week.

It was not immediately clear why N'Tchama might have carried out the assault, but the captain is also a former associate of the government overthrown in the April coup.

Meanwhile another member of the "Red Berets" shot himself on Monday, unit leader Major Julio Nhate told AFP.

"We don't yet know the reasons for his suicide but we have opened an inquiry which will determine the motive for his act," he said.

The deceased soldier was close to the six who were killed during the October 21 attack, according to several of his colleagues.

One of them, speaking on condition of anonymity, said they were all of the same ethnicity from the northern Cacheu region.

The latest coup bid has caused further turmoil in the west African nation which has suffered chronic instability since independence from Portugal in 1974 due to conflict between the army and state.