Sept 28 (Reuters) - Warren Buffett's Berkshire Hathaway Inc (BRKa.N) bought another 5.99 million shares of Occidental Petroleum Corp (OXY.N), boosting its stake to 20.9% after the oil company's shares lost about a fifth of their value in less than a month. The purchases were made between Sept. 26 and Sept. 28 and cost about $352 million, Berkshire said in a regulatory filing on Wednesday. Following the purchases, Berkshire now owns about 194.4 million Occidental shares worth approximately $11.9 billion, based on Occidental's Wednesday closing price of $61.41. Register now for FREE unlimited access to Reuters.com RegisterBerkshire had gone seven weeks since its last purchase of Occidental shares, which pushed its stake above 20%. Occidental's share price has more than doubled this year, benefiting from rising oil prices following Russia's Feb. 24 invasion of Ukraine.

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