Occidental Petroleum OXY.N climbed 7.4% after Warren Buffett's Berkshire Hathaway BRKa.N disclosed buying more shares of the oil company this week. U.S. stocks have swung wildly this week on fears that the Ukraine war, surging inflation, COVID-19 lockdowns in China and a hawkish Federal Reserve policy could spark a global economic slowdown. Fed Chair Jerome Powell repeated on Thursday his expectation that the central bank will raise interest rates by half a percentage point at each of its next two policy meetings while pledging that "we're prepared to do more" if data turns the wrong way.