TOKYO, Feb 25 (Reuters) - Billionaire investor Warren Buffett's Berkshire Hathaway has raised its stake in Japan's top five trading firms to around 9%, it said in its annual report.

Berkshire Hathaway's wholly owned subsidiary National Indemnity Company previously held about 7% to 8% in Mitsubishi Corp, Itochu Corp, Mitsui & Co, Sumitomo Corp and Marubeni Corp, according to filings made in June.

Berkshire first announced its stakes in the trading houses in 2020 with the intention of holding them long-term and increasing them to as much as 9.9%.

Bershire Hathaway said in the report, dated Feb. 24, that it paid 1.6 trillion yen ($10.63 billion) for the five stakes, which were valued at 2.9 trillion yen at the end of 2023. In dollar terms, that translated to unrealised gains of 61% or $8 billion, it said. ($1 = 150.5000 yen) (Reporting by Makiko Yamazaki and Shinichi Uchida Editing by Chang-Ran Kim)