(Adds Penn Virginia's response)
June 25 (Reuters) - Penn Virginia Corp's shares roseas much as 23 percent on Thursday following a report that BP Plc had offered to buy the U.S. oil and gas producer for $8per share.
The offer, which values the company at about $573 million,represents an 80 percent premium to Penn Virginia's Wednesdayclose of $4.45. The company's shares rose as much as $5.47.
Penn Virginia has rejected the offer, saying it undervaluesthe company, financial news website Proactive Investorsreported, citing sources familiar with the situation. (http://bit.ly/1eJjp4g)
BP and Penn Virginia declined to comment. (Reporting by Anannya Pramanick in Bengaluru; Editing bySaumyadeb Chakrabarty)
BP (BP.)