Activist investor Carl Icahn has increased his stake in financially troubled oil and natural gas company Chesapeake Energy (NYSE:CHK) to nearly 9%, according to SEC documents filed today. Since Nov. 12, Icahn has acquired 9.6 million Chesapeake shares under various funds and entities, according to the SEC filing, including 3 million shares just yesterday.

In all, Icahn owns almost 60 million shares, or nearly 9%, of Chesapeake Energy. The aggregate purchase price of the shares was $951 million, according to today's filing. Icahn is famous for being a "corporate raider," taking interests in companies he believes to be poorly managed, and subsequently pushing for shake-ups at the higher levels. He's already been pushing for change at Chesapeake, when his stake earlier this year was at 7.6%.

Chesapeake's stock was trading more than 1% higher around lunchtime on Tuesday.