Three London homes worth more than £80m have been frozen by the High Court in the second-ever use of anti-corruption orders to stop foreigners laundering cash in the UK.
The Unexplained Wealth Orders (UWOs) were sought last week against a foreign official who was not named in court.
The National Crime Agency has demanded that the subject of the probe explains the source of their wealth.
The homes cannot be sold or given a new owner until the investigation is over.
The properties are held by offshore companies.
UWOs are a new anti-financial crime power targeted at foreign government officials and their families from outside the European Economic Area (EEA) who are believed to have laundered stolen money through British property.
If the suspect – known as a “politically exposed person” – cannot explain the source of the wealth, the NCA can ask the High Court to order the homes’ seizure.
The measure aims to target people who have committed huge frauds and embezzlements abroad where there is little or no chance of obtaining the evidence to convict them in a British court.
The first ever UWO was used against Zamira Hajiyeva, the wife of a jailed Azerbaijan banker, who lives in a £12m London home and owns a Berkshire golf course.
Court papers disclosed to the BBC on Tuesday revealed how she spent £16m in Harrods over a decade without raising suspicions.
That legal action has so far lasted 15 months – and she not only denies wrongdoing but is also appealing against the potential loss of her property.
In a statement, the NCA said the three more recent orders were against property in “prime locations” in the capital.
Andy Lewis, the NCA’s head of asset denial, said UWOs are a “powerful tool in being able to investigate illicit finance flowing into the UK and discourage it happening in the first place”.
“The individuals behind these offshore companies now have to explain how the three properties were obtained,” he said.
By Dominic Casciani, BBC home affairs correspondent
Unexplained Wealth Orders have caught the public’s eye because of the extraordinary allegations of mysterious wealth hidden behind the doors of some of Britain’s mansions.
But the fact is that the cases so far brought by the NCA are probably the tip of an iceberg of suspected corruption.
Of the properties owned by overseas companies in England and Wales, two-thirds are registered to firms in the British Virgin Islands, Jersey, Guernsey and the Isle of Man – which means it can be difficult to work out who ultimately benefits from the asset
The government is supposedly committed to banning the ownership of British property through shadowy companies – but nothing has been done.
Until there is more clarity on who owns what, already-stretched financial crime investigators will struggle to seize the suspected billions of stolen loot washing around the British property market.
Robert Barrington, executive director of campaign group Transparency International, welcomed the latest UWOs – but said much more needed to be done.
He said: “London has long been the playground of the world’s corrupt kleptocrats and oligarchs – it’s very encouraging to see that this is at last being challenged.”
“Two years ago we identified £4.4bn worth of UK property bought with suspicious wealth. From that list of around 150 cases, two have now been progressed.”
He said the two cases represent “progress” but are “still an insufficient response to the magnitude of the problem”.