Austrian police have arrested Dmytro Firtash, 48, a Ukrainian gas industry oligarch, in Vienna.
According to Reuters, government sources say that the gas industry magnate, also known as Dmitry, is in police custody under the Federal Criminal Agency's (FCA) orders.
He has been under investigation by the US Federal Bureau of Investigation (FBI) since 2006.
While the FCA has not confirmed the name of the detainee in question, it identified suspect only as Dmitry F.
"Based on years of investigations by the US FBI and an arrest warrant issued by a US federal district court, Vienna prosecutors issued a national order to detain the businessman," said the FCA in a public statement.
The agency added that he was arrested on the suspected violation of bribery laws and forming a criminal organisation.
Firtash is one of the top ten richest men in Ukraine and is tipped to be worth around $1bn (£599m, €717m) and is the co-owner of RosUkrEnergo, which controls most of Ukraine's lucrative titanium business.
Firtash acquired chemicals plant Stirol in Donetsk in the aftermath of Yulia Tymoshenko losing out to Viktor Yanukovych in the 2010 presidential election.
During the same year, he won an international arbitration court ruling, which forced Ukraine's state gas company to hand over around $3bn of gas.
Over the last three years, dissidents have suggested that Yanukovych's inner circle handed Firtash more influence over the country than Ukraine's richest man, Rinat Akmetov.
Famously, in a Wikileaks cable dated December 2008, Firtash confirmed to then US Ambassador to Ukraine William Taylor, that he once had ties with alleged Russian mafia boss Semyon Mogilevich.
Taylor quoted Firtash in the cable saying that "he needed, and received, permission from Mogilevich when he established various businesses, but he denied any close relationship to him."
Firtash then denied any links in an official statement later on.
More details to follow.