The Ukrainian crime gang used offshore firms in British tax havens to secretly invest millions of pounds in the UK, a BBC Panorama investigation has found.
The gangsters, and in some cases their family members, bought luxurious property in prime London locations, including a flat worth £12.5m.
A daughter of a man dubbed the "Don of Odessa" is the registered owner of three homes in one of the most expensive blocks.
Many of the revelations come from the Paradise Papers data breach.
The gang were from the Black Sea port of Odessa and made money in the oil industry.
They came on to the police's radar in the late 1990s when they were suspected of drugs and arms smuggling. In the chaos following the collapse of the Soviet Union the gang branched out into Europe, using Italy as a base.
But police were on them. For four years anti-mafia specialists' officers tracked their movements across the continent. They tracked their phones and the things discussed were chilling, police said.
"They described murders that were particularly cruel. 'I kept hitting his head until it broke... I killed him with many blows,'" recalls Italian state police Deputy Commissioner Nunzia Savino. "They were extremely violent."
The gang was organized along strict mafia lines with each member assigned a role.
Among them were:
Alexander Angert, nicknamed the "Don of Odessa". Police say he was once jailed for murder
Nickolay Fomichev described as a "violent and armed person"
Hennady Trukhanov, the man who trained members of the gang in "hand-to-hand combat and sniper shooting with high precision weapons", according to Ms. Savino. He is now the mayor of Odessa.
They and six more officials of the Odesa city council are suspected of embezzlement by malversation.
The court demanded to detain Trukhanov and Vugelman as a preventive measure, but some MPs stood bail for them, so they were released.
The NABU began the investigation of this case in November 2016 because the city council purchased former plant 'Krayan' at an overvalued price. According to the bureau, the building was sold for $149, 080 at the beginning of 2016 and then the Mayor office of Odesa purchased it in September 2016 for $6.9 million.