TBILISI, Georgia (Bloomberg) - UK police are treating as "suspicious" the death of Badri Patarkatsishvili, a Georgian businessman accused of plotting a coup against pro-Western President Mikheil Saakashvili.

Mr. Patarkatsishvili, a business partner of fugitive Russian billionaire Boris Berezovsky, died at age 52 in the county of Surrey, near London late yesterday of a suspected heart attack.

"All unexpected deaths are treated as suspicious and a postmortem will be held later today to establish the cause of death," a spokeswoman for the Surrey police said by telephone yesterday. "If this isn't conclusive, further tests will be necessary. A number of lines of inquiry are being followed, and this includes reviewing his recent movements."

Mr. Berezovsky said Mr. Patarkatsishvili's death is a "terrible tragedy."

"I have lost my closest friend. This is a huge loss for all of his family and friends," he said in an e-mailed statement. Mr. Berezovsky made no comment on the circumstances of the death.

Mr. Patarkatsishvili made his fortune as Mr. Berezovsky's partner in Russia during the 1990s. He was a senior executive at car dealer LogoVAZ and later at the ORT television station. In 2006, he briefly owned the Kommersant publishing house.

Mr. Berezovsky said in an interview last November that Mr. Patarkatsishvili was in charge of all his assets in Russia. "I continue to make money, but I passed all my businesses to my partner, to Badri," Mr. Berezovsky said. "I sold everything and he's controlling everything."

Mr. Patarkatsishvili said in November that the Georgian government was trying to kill him.

"I believe they want to kill me by hiring Chechen hit men to eliminate me," he said in comments broadcast on his Imedi television station. "I have nearly 120 bodyguards and I still don't feel safe." The government has not responded to Mr. Patarkatsishvili's allegation.

The Georgian businessman, along with Mr. Berezovsky, faced fraud charges in Russia for his role in the alleged theft of more than 2,000 cars from OAO AvtoVAZ in the mid-1990s. Georgian authorities issued an arrest warrant for Mr. Patarkatsishvili last month on charges of plotting a coup and planning a "terrorist attack" on a government official. He denied all of the charges against him.

Keti Akhalkatsi, a spokesman for the Georgian Prosecutor General's Office, said the charges against Mr. Patarkatsishvili could not be dropped until confirmation of his death is received from London.

Mr. Patarkatsishvili ran against Saakashvili in the former Soviet republic's presidential election last month.

Georgian opposition leader Irakli Okruashvili, a former defense minister now in Paris, where he is seeking asylum, said Mr. Patarkatsishvili's death would change the Black Sea country's political landscape. "He was an important player," Mr. Okruashvili said by telephone.

Mr. Patarkatsishvili returned to Georgia in 2001 and founded Imedi. He gave control of the media company to Rupert Murdoch's News Corp. on October 31 after saying he would fund the opposition and enter politics. He also formed close ties with then President Eduard Shevardnadze.

"I brought him to Georgia," Mr. Shevardnadze said by telephone. "He was wanted in Russia. He felt safe here."

"I can't comment on the recent allegations against him. His move into politics is beyond me," Mr. Shevardnadze said. "I don't want to rely on media reports. I can say that he was smart and talented, but that he also had a few tricks up his sleeve."

When Mr. Saakashvili came to power in the so-called Rose Revolution in 2003, Mr. Patarkatsishvili became an ally. Their relationship soured in 2006.

"The confrontation with Saakashvili started because Patarkatsishvili couldn't get what he wanted: total control of Georgia's economic and business life," Alexandre Rondeli, head of the Tbilisi-based Georgian Foundation for Strategic and International Studies, said by telephone. "He wanted to buy practically everything. When he didn't get this, he showed his other side in politics."