Nicolas Labre Pereira de Jesus, known by his nickname 'Fat Family', had been interned at the hospital since last Monday when he had been injured during a confrontation with police in the nearby Morro Santo Amaro favela , but he was freed during a shootout

One person was killed and two were wounded after a fierce gunfight broke out inside the Rio de Janeiro hospital which will treat visitors and athletes to the Olympic Games.

A gang of 25 men armed with semi-automatic rifles, pistols and hand grenades invaded the Souza Aguiar hospital to rescue a drugs baron who was being treated under armed police guard.

Terrified patients and staff were caught in the crossfire as the gunmen stormed the facility, in Rio's city centre, at 3.15am on Sunday morning.

A patient who was in the hospital at the time, Ronaldo Luiz de Souza, died after being hit by a stray bullet, while an on-duty nurse was also shot and is in a serious condition.

A military policeman was also hit during the shooting and is understood to have undergone surgery and been discharged.

Hospital walls and equipment were also damaged in the hail of automatic gunfire as the assailants rampaged through the facility, while a police car parked outside was blown up by a home-made bomb, according to reports.

Police said the gang, who arrived in a fleet of five cars and four motorbikes, took a street seller hostage before splitting into two groups, one of which took over the hospital's reception area while the other made their way to the sixth floor, to rescue the drug lord.

Souza Aguiar hospita, pictured, is one of five hospitals designated by the city to treat tourists during the sporting event because of its proximity to the famed Maracana Stadium, site of the opening ceremony

Nicolas Labre Pereira de Jesus, known by his nickname Fat Family, had been interned at the hospital since last Monday when he had been injured during a confrontation with police in the nearby Morro Santo Amaro favela.

His brother Marco Antonio da Silva, another drugs baron known as My Thor, is believed to have led the military-style operation to free him.

Although police had reportedly received intelligence warning about the planned rescue attempt, there were still only two policemen guarding De Jesus at the time of the attack.

Military policeman Fabio Melo, who was guarding the drug lord at the time of the attack, told a local newspaper: 'Thanks be to God I managed to get out unharmed.

'But you know how it is, right? We are unprotected. I'm unprotected, you are unprotected. The whole of the population.'

Brazilian federal police officers close the road during the security drill for the transfer of athletes at Maracana Stadium which will host football matches for Rio 2016 Olympic games in Rio de Janeiro

Police acknowledged that they had received reports last week about a plot to free the suspected drug trafficker

The incident comes just 46 days before the start of the Olympic Games, during which the Souza Aguiar hospital will be the principal facility treating foreign visitors who become ill or suffer accidents.

The hospital was recently refurbished with air conditioning throughout, and received new surgical equipment to cater for Olympics visitors.

The attack occurred just days after the state government of Rio de Janeiro declared a 'state of calamity' over lack of finances and warned that the situation could impede the city's ability to meet its Games commitments.