Georgian businessman Badri Patarkatsishvili, who feared assassination and faced accusations of plotting a coup in his homeland, has died in Britain and British police are treating his death as suspicious.

Police said checks had found no radioactive traces on Patarkatsishvili's body or at his home. Former Russian spy and Kremlin critic Alexander Litvinenko died in November 2006 after being poisoned with radioactive polonium in London.

Georgian public television said Patarkatsishvili, who was a critic of President Mikhail Saakashvili and ran against him in a presidential election last month, had died of a heart attack at his mansion near London.

But a source close to Patarkatsishvili said the 52-year-old billionaire had feared for his life and allies in the former Soviet republic called for an international inquiry.

Police said they had referred the case to a major crime investigation team.

An ambulance was called to his secluded mansion late on Tuesday after Patarkatsishvili had entertained a large number of friends and family, police said.

"As far as I know from his relatives, it was his heart," exiled Russian billionaire Boris Berezovsky, a friend and business partner, said by telephone.

Patarkatsishvili had lived in Britain since late last year, when Georgian authorities accused him of plotting a coup against the president and issued a warrant for his arrest.

He ran as a candidate in Georgia's presidential election on January 5 and won about 7 percent of votes, but did not campaign in his homeland for fear of detention.

"His death is a big loss for our country. I know he wanted to do a lot of good things for Georgia," Eduard Shevardnadze, a former Georgian president and Soviet foreign minister, said.

Patarkatsishvili showed no signs of illness at a meeting in London on Tuesday, someone who attended the meeting said.

"As the result of initial work by experts there is no suggestion of anything radioactive involved," a police spokeswoman said on Wednesday.

Patarkatsishvili's body has been taken to a hospital for a post-mortem and results are not expected until Thursday.

LEGAL CHARGES

Georgian government officials declined comment on the death.

Rati Shartava, a Tbilisi-based aide to Patarkatsishvili, said his death was triggered by legal charges brought by the government, Russia's Interfax agency reported.

"The state machine fought him and his heart gave in," Shartava said.

Western powers watch developments in Georgia closely. It lies on the route of an oil pipeline in a strategic region bordering Turkey and Russia, and is at the heart of a tussle for influence between Moscow and new allies in the West.

Patarkatsishvili made his fortune in Russia during the 1990s in association with Berezovsky.

Following Georgia's election, which the opposition said was rigged and on which Western monitors gave a mixed verdict, a Georgian court seized his television station and other assets.

Georgian authorities blamed Patarkatsishvili and his Imedi television station for stirring protests against Saakashvili in Tbilisi last November, the biggest challenge to the pro-Western president since he took power in 2003.

The protests were crushed when Saakashvili sent in riot police to fire rubber bullets and tear gas at demonstrators.

Opposition leaders said the protests were triggered by anger at corruption and poverty. Patarkatsishvili accused Saakashvili, who promoted an image abroad of a modern, pro-Western leader, of pushing his country into dictatorship.