Guinea Bissau's military on Saturday arrested the man accused of being the mastermind behind an attack on an elite army barracks a week ago which the government said was an attempted coup.

Soldiers gathered at army headquarters in Bissau as Captain Pansau N'Tchama was paraded in, throwing a Portuguese flag over his shoulders in apparent reference to accusations the former colonial ruler instigated the foiled coup.

N'Tchama was accompanied by seven heavily armed soldiers, wearing only a shirt and boxer shirts with his hands and bare feet tied.

The captain accused of leading the October 21 attack in Bissau was arrested on Saturday morning with two suspected co-conspirators in Bolama, the capital of the Bijagos archipelago on the closest of the islands to the Bissau.

General Tomas Djassi said he had lead a unit of 158 men in the hunt for N'Tchama.

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

Transition authorities in the west African nation have accused 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.

Several other arrests were made at the headquarters of Gomes' party in the wake of the attack.

Two politicians seized by soldiers were found badly beaten in the countryside on Tuesday, and the interim government distanced itself from what it called "isolated acts of physical brutality."

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.

That putsch interrupted a presidential election between the first and second rounds, which Gomes was leading after the initial vote.

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.

No president has ever completed a full term in office.

Coups, counter-coups and regular assassinations have also made the unstable nation an attractive destination for South American druglords seeking a hub to move cocaine into Europe.

A transitional administration has taken over with elections planned for an unspecified date in 2013.