Penn Virginia Corp’s shares rose as much as 23 percent on Thursday following a report that BP Plc had offered to buy the U.S. oil and gas producer for $8 per share.

The offer, which values the company at about $573 million (£364 million), represents an 80 percent premium to Penn Virginia’s Wednesday close of $4.45. The company’s shares rose as much as $5.47.

Penn Virginia has rejected the offer, saying it undervalues the company, financial news website Proactive Investors reported, citing sources familiar with the situation.

BP and Penn Virginia declined to comment.

Extracted in full from Yahoo.