Troops in Guinea-Bissau clashed with renegade forces overnight, leaving at least one soldier dead as they combed the capital following an alleged failed coup, an army officer said Tuesday.

"We had gone to Luanda (district) to arrest a group of suspects," an army captain told AFP on condition of anonymity. "They were armed and opened fire on my men; I lost one and two others were wounded."

Soldiers deployed in the streets of Bissau on Monday, some of them demanding better pay, after attacking the headquarters of general staff and seizing weapons from the gun shop.

A raid on the home of a lawmaker thought to be harbouring mutineers turned up a "veritable arsenal" of weapons, Interior Minister Fernando Gomes said.

EU foreign policy chief Catherine Ashton condemned the violence.

Ashton "is deeply concerned by yesterday's violent actions in Guinea-Bissau by some elements within the military," a spokesman said in statement Tuesday. "She condemns in the strongest possible terms such anti-constitutional actions. ... Violent attempts against constitutional legality cannot be allowed, and must stop."

A manhunt was being carried out jointly by soldiers, police and paramilitary police, military sources said.

"There will be investigations, and those identified will be brought to justice," Foreign Minister Mamadu Djalo Pires said as he briefed diplomats on the unrest, which took place as President Malam Bacai Sanha was receiving medical treatment in Paris.

The head of the armed forces later said the navy chief -- Rear Admiral Jose Americo Bubo Na Tchuto, who has previously been accused of involvement in coup plans and in the drugs trade -- was arrested over what he described as a coup attempt.

Long thought close to army chief of staff General Antonio Indjai, Bubo Na Tchuto had reportedly fallen out with him, and some observers surmised that the unrest involved a settling of scores.

The captain said his unit had moved in to arrest a group that included lawmakers and former ministers of the ruling African Party for the Independence of Guinea and Cape Verde (PAIGC) who are reportedly opposed to Prime Minister Carlos Gomes Junior.

An officer said two of the lawmakers, Francisco Conduto De Pina and Roberto Cacheu, were spotted in a southern district of Bissau but got away amid the shooting.

Cacheu was thought to be harbouring some of the mutineers, and security forces fired rockets at his home, leaving some of the walls pockmarked and burnt, an AFP journalist reported.

Gomes told reporters of the siege: "They (the mutineers) opened fire on one of our soldiers when he went through the door. His comrades returned fire, there were a lot of explosions because of grenades and other munitions stockpiled in the house."

He added: "It was a veritable arsenal."

A fierce exchange of fire that lasted close to three hours also erupted in the seaside capital's Antula neighbourhood overnight, military sources and witnesses said.

"In Monday morning's attack, many soldiers were able to make away with weapons and ammunition. My task was to recover the weapons and arrest the suspects," another military commander said.

"But they offered resistance and I had to resort to heavy equipment, including bazookas," he said, without elaborating on the identity of the suspects or any casualty toll.