Five convicts escaped from a high-security penitentiary in Portugal, in what the authorities said was a well-planned prison break.

The inmates reportedly had help from outside to climb over and down a 6-meter-high wall, authorities say.

Police warned the public that the escaped convicts were dangerous, releasing their images to help identify them.

The inmates waited for the moment when they knew the guards would be concentrating on monitoring visits to the prison, and within a few moments had made their escape.

Outside, they had two cars and three accomplices waiting for them.

The prison lacked towers that provided a view of the courtyard, which authorities say was fundamental to the escape plan.

"The Portuguese state decided half a dozen years ago to deactivate the towers of Vale de Judeus, even demolishing them. In the past, that prison had four towers and a permanent guard in each tower," said Frederico Morais, President of the Prison Guard Union.

Authorities are on alert and say that “international cooperation” has been “sped up”.

Throughout Saturday night, the judicial police searched inside the prison itself. The aim was to gather information such as the visitation records and telephone calls of the fugitives who are still at large.

Dangerous individuals

The five prisoners who escaped from Vale de Judeus were identified as Fábio Fernandes Santos Loureiro (33), Fernando Ribeiro Ferreira (61), Rodolf José Lohrmann (59), Shergili Farjiani (40) and Mark Cameron Roscaleer (39): two Portuguese citizens, an Argentine, a Georgian and a British national.

Loureiro was sentenced to 25 years in prison for the crimes of trafficking in minor quantities, criminal association, extortion, money laundering, insult, aggravated theft, resisting and coercing an official and driving without a legal licence.

Ferreira was also sentenced to 25 years for drug trafficking, criminal association, theft, robbery and kidnapping;

Lohrmann was serving 18 years and 10 months for criminal association, theft, robbery, false declarations and money laundering. He is also suspected of the murders of at least two children of prominent politicians in Argentina.

Roscaleer was serving nine years for kidnapping and robbery. Farjiani was given seven years for theft, violence after the theft, and forgery of documents.

"If you come across these prisoners, don`t try to interfere with them; call 112 because these are individuals who have no problem killing people in order to escape," said Morais.