Bloomberg reports that Russian oligarch Alexander Mamut has increased his stake in HMV Group, the British company which owns and operates leading U.K. entertainment retailer HMV.

According to Bloomberg, Mamut has upped his existing stake in HMV Group -- which also owns the Waterstone's chain of bookstores and HMV's live music business - to more than 3%.

Earlier this year, Forbes Magazine estimated Mamut's net worth to be $1.5 billion. HMV Group's share price has fallen 49.08% year-to-date and was £0.46 ($0.74) per share at the time of going to press.