Austria arrested one of Ukraine's richest men, a fresh twist for the one-time ally of ousted pro-Russian president Viktor Yanukovych.

Gas magnate Dmytro Firtash was taken into custody over alleged links to organised crime in Spain, moments after a Vienna court ruled he could be extradited to the US on corruption charges.

Firtash, 51, made money through connections with Russian gas giant Gazprom, and was at one time linked to a former campaign aide of US President Donald Trump.

He is wanted in the US over charges that he and five others paid $18.5 million in bribes to officials in India to secure titanium mining licences in 2006.

The United States argues it has jursidiction because the conspiracy involved using US financial institutions, travel to and from the US, and use of US-based communications -- computers, telephones, and the internet.

Firtash was arrested in Vienna in March 2014, but released on a record Austrian bail of 125 million euros ($130 million).

He has denied all charges and maintained he was the victim of a smear campaign.

His legal team argued that he was caught up in a larger battle over the future of Ukraine, where the government has been engaged in bloody fighting with Russian-backed separatists in the east since 2014.

Authorities in Barcelona issued a European arrest warrant in November 2016, with media reports saying Firtash was accused of belonging to a criminal organisation which had laundered 10 million euros ($10.5 million) in Spain.

But when the warrant was issued, the tycoon was already under house arrest in Austria over the US allegations.

A lower court in Vienna sided with the tycoon in April 2015 and rejected the US request.

But the appeals court said Tuesday the US had provided "sufficient" proof that Firtash "may have committed the crimes he is accused of".

The prosecutor's office refused to comment on the Spanish case or how Firtash's arrest would affect the extradition ruling.

Austria's Justice Minister Wolfgang Brandstetter told broadcaster ORF the extradition would not be implemented until a court had reviewed the Spanish case.

- Vladimir Putin -

Firtash owns Group DF, a business empire involved in energy, chemicals, media, banking and property in Ukraine and other countries including Germany, Italy and Austria.

He made his fortune importing gas to Ukraine from Russia and Central Asia via his group Rosukrenergo, since disbanded, in collaboration with Russian gas giant Gazprom.

Having backed the 2010 election campaign of Yanukovych, Firtash was able to expand his business interests, acquiring chemicals and fertiliser factories as well as TV channel Inter.

The Russian-backed Yanukovych was ousted in protests in February 2014, and Firtash's arrest in Austria came soon afterwards, although officials deny any link.

Observers say US authorities want to detain Firtash because he holds information on close allies of Russian President Vladimir Putin.

"The case against Firtash in the United States will not be limited only to the bribery allegations in India," said Ukrainian MP Sergiy Leshchenko, a former journalist who has investigated Firtash's case.

"He is very valuable not only as a defendant but as witness too."

Although Tuesday's ruling cannot be appealed, the final extradition decision lies with the justice minister.

Firtash's lawyer slammed Tuesday's extradition ruling, saying "appropriate steps" would be taken to overturn it.

"Mr Firtash categorically rejects all allegations and maintains that this all relates to US political persecution," said Dieter Bohmdorfer in a statement. "We remain confident that Mr. Firtash’s innocence will be proven."

source: AFP