TOKYO, Sept 1 (Reuters) - Japan's Nikkei share average was almost unchanged on Tuesday, as investors booking profits was countered by an extended rally in stocks of trading companies.

The benchmark Nikkei share average was up 0.03% at 23,145.86 by the midday break, after flitting between positive and negative territories in early trade. There were 71 advancers against 149 decliners.

The broader Topix fell 0.23% to 1,614.40, with all but eight of 33 sectoral sub-indexes on the Tokyo exchange trading lower.

Shares of trading firms continued to rally from the previous session after Warren Buffett's Berkshire Hathaway said it bought a 5% stake in each of Japan's five biggest trading houses, together worth over $6 billion.

Mitsubishi Corp gained 2.85%, Mitsui & Co rose 1.85%, and Sumitomo Corp added 1.27%. Marubeni and Itochu Corp rose 1.19% and 0.94%, respectively.

Shares of Sojitz also followed suit to add 0.82%.

Broader sentiment received some boost following data that showed factory activity in China expanded at the fastest clip in nearly a decade in August, bolstered by the first increase in new export orders this year.

Back home, data showed Japan's jobless rate increased, the availability of jobs in July declined, and the country's factory activity contracted at the slowest pace in six months in August.

Life insurers, which rely on foreign bonds for income, dipped taking overnight cues from lower long-term U.S. Treasury yields.

T&D Holdings dropped 1.35% and Tokio Marine Holdings fell 1.31%, while Sompo Holdings lost 1.01%.

Elsewhere in the market, the Mothers Index of start-up firm shares rose 1.89% to 1,142.82. (Reporting by Eimi Yamamitsu; editing by Uttaresh.V)