Security tight at Berezovsky home

Security is tightened near the British home of Boris Berezovsky, after the Russian oligarch was found dead there on Saturday (March 24).

Police are treating his death as "unexplained" and a full investigation is underway at the house in Ascot.

Russian media speculate that the 67-year-old may have committed suicide or suffered a stress-related heart attack.

Berezovsky was humiliated last year when he lost a $6 billion legal battle against Roman Abramovich.

SOUNDBITE: (English) BORIS BEREZOVSKY IN AUGUST 2012, SAYING:

"I absolutely amazed at what happened today. I'm surprised, completely."

Some associates say he had become depressed as he grappled with the financial impact.

The tycoon once helped Vladimir Putin rise to power in the Kremlin, but then became one of his fiercest critics.

In 2000, he fled to Britain seeking asylum.