British authorities on Monday launched a money- laundering investigation linked to possible corruption in Ukraine and froze $23 million (17 million euros) in assets.
The announcement came a day before international talks in London aimed at recovering assets which may have been looted under the regime of deposed pro-Moscow president Viktor Yanukovych.
Britain's Serious Fraud Office (SFO) said it had "opened a criminal investigation into possible money laundering arising from suspicions of corruption in Ukraine."
"The SFO has obtained a restraint order freezing approximately $23 million of assets in the UK in connection with this case."
It said it could not provide more details for reasons of confidentiality.
The two-day asset recovery talks starting on Tuesday will be hosted by British interior minister Theresa May, U.S. Attorney General Eric Holder and Ukraine Interior Minister Arsen Avakov.
Senior government officials, prosecutors and representatives from financial centres and international organisations will also attend, Britain's Home Office said.
Several countries are helping Ukrainian-led investigations into alleged corruption and money laundering by members of Yanukovych's government.
Swiss authorities have ordered a freeze on the assets of both Yanukovych and his multi-millionaire son Oleksandr, as well as 18 other former ministers and officials.
Yanukovych was ousted in February following a series of massive protests after he decided to scrap an agreement with the European Union in favour of closer ties with Russia.
He fled Ukraine for Russia.
[Image via Agence France-Presse]