According to Commissioner Afonso Sousa, from the Porto PSP Criminal Investigation Division, the group was “improving” in the assault on “oversized” column vaults, and in particular stole money and jewellery.

"He was working on robberies in establishments in Porto and did a thorough and preliminary study of the places to be robbed," he added, explaining that although the safes were the main target, they ended up stealing other goods.

In the group, there were “perfectly defined functions”, with a hard core responsible for the robberies, and the others participated in the sale of the theft product, the source said.

All robberies were completed at night or early in the morning.

During one of the robberies, which took place on the public highway in Vila Nova de Gaia, an 82-year-old man died in a case whose investigation was carried over to the Judiciary Police.

The PSP explained that there is not yet the result of the autopsy, but its "belief" is that the octogenarian was not killed by the robbers, but the victim of a health problem.

The detainees are eight, seven men, between 52 and 62 years old, and a woman of 47 years.

In 15 assaults that have already been attributed to him by the investigation, the group has profited between 150,000 and 200,000 Euros, said Commissioner Afonso Sousa, who believes, however, that the group has consummated other thefts and robberies.

The group's dismantling operation was launched on 24 November and involved more than 100 professionals from PSP's Criminal Investigation Division, Special Police Unit and Rapid Intervention Teams.

Thirteen home search warrants were fulfilled, four in other locations and five in vehicles in the cities of Porto, Gondomar, Matosinhos, Santa Maria da Feira and São Pedro do Sul.

Among the material seized are articles of sacred art, safes, fur coats, computers, electric and conventional weapons, electronic equipment inhibiting alarm systems, tools used to break the safes, among others.

The operation followed an investigation initiated five months ago.