Warren Buffett's Berkshire Hathaway boosts Occidental Petroleum holdings to $8.8 billion, lifting stake in oil giant to 15.2%

• Warren Buffett's Berkshire Hathaway boosted its stake in Occidental Petroleum to $8.8 billion this week.
• Occidental stock rose as much as 4.7% Thursday to $64.49, its highest mark in three years.

Warren Buffett's Berkshire Hathaway bought an additional 5.9 million shares of Occidental Petroleum on Monday and Tuesday this week, the company said in a Wednesday regulatory filing.

In total, the new shares cost about $336 million, boosting the firm's holding to 142.3 million shares worth about $8.8 billion.

The company now holds a 15.2% stake in the energy giant.

Occidental stock rose as much as 4.7% Thursday to $64.49, its highest level in three years.

"Occidental is generating tons of free cash flow and using it to pay down debt, repurchase shares, and pay dividends to shareholders – of which Berkshire is now the largest," Darren Pollock, portfolio manager at Cheviot Value Management told Insider previously.

Buffett has been on a buying spree as of late, making or agreeing to about $23 billion worth of investments in recent weeks with companies including HP, Alleghany, and Occidental.