Dec 13 (Reuters) - Best Buy Co Inc founder Richard Schulze is expected to make a fully financed offer to buy the consumer electronics retailer by the end of the week, the Minneapolis Star Tribune reported late Wednesday, citing a source.

Schulze's bid would be at least $5 billion to $6 billion, the newspaper reported, citing the source. Best Buy declined to comment on the report.

Best Buy shares were up 12.2 percent to $13.66 in premarket trading.