Still a mystery: The death of Putin nemesis Boris Berezovsky remains unsolved in England

British police refused to rule out foul play Sunday in the unexplained death of exiled Russian business tycoon Boris Berezovsky — a chief nemesis of Kremlin leader Vladimir Putin.

Detectives do not believe chemical or radioactive poisoning did in the 67-year-old oligarch, but the notion of a sinister assassination plot provoked wild speculation sweeping the globe.

“We are acutely aware of the level of interest into his death and are focused on conducting a thorough investigation as we would with any unexplained death,” Detective Chief Inspector Kevin Brown said Sunday.

“We do not have any evidence at this stage to suggest third-party involvement,” said Brown, adding that Scotland Yard officials are awaiting the results of an autopsy.

Berezovsky, who sought asylum in Britain in 2000 after Putin’s government moved to prosecute him on fraud, embezzlement and money-laundering charges, was found dead Saturday in a locked bathroom of his Ascot, England, home.

Just 48 hours earlier, he said in an interview with the Russian edition of Forbes magazine, “There is no point in my life.”

“I don’t want to be involved in politics. I don’t know what to do,” he told the magazine. “I’m 67 years old. And I don’t know what I should do from now on.”

He added that he was homesick for Russia.

“I want nothing more than to return to Russia,” he told Forbes. “Even when they opened a criminal case against me, I wanted to return to Russia. . . . That was my main miscalculation: that Russia is so dear to me that I cannot be an emigre.”

Hours after his death, Putin’s press secretary revealed Berezovsky had written to the Russian president asking for forgiveness and the ability to return home.

Berezovsky had accused Putin of being personally involved in the 2006 death of ex-KGB spy Alexander Litvinenko, who was poisoned in London with tea spiked with radioactive polonium-210.

Litvinenko was granted asylum in England after accusing superiors in the Russian secret service of plotting Berezovsky’s murder.

Like Berezovsky, Litvinenko had also accused the secret service of blaming Chechen rebels for bombings and other terrorist acts it staged in an effort to bring Putin to power.