Billionaire Warren Buffett's Berkshire resumes buying Phillips 66 stock

Berkshire previously invested in ConocoPhillips <COP.N>, which spun off Phillips 66 in 2012. (Warren Buffett, Berkshire Hathaway CEO, uses a listening device as he listens to Chinese President Xi Jinping at a U.S.-China business roundtable, comprised of U.S. and Chinese CEOs in Seattle, Washington September 23, 2015. REUTERS filepic)

NEW YORK: Berkshire Hathaway Inc, the conglomerate run by Warren Buffett, has resumed its purchases of Phillips 66 stock, and spent roughly US$832 million in January to boost its stake even as the oil refiner's profit margins narrowed.