TOKYO, Sept 30 (Reuters) - Japan's Nikkei share average

fell on Tuesday as investors adjusted their portfolios and

corporates stayed away from buybacks at the end of the first

half of the nation's fiscal year.

As of 0145 GMT, the Nikkei was down 0.1% at

44,996.05. The broader Topix edged down 0.08% at

3,128.46.

"Today's decline does not mean the market sentiment has

weakened. This kind of adjustment associated with the end of the

first half of the year may continue tomorrow," said Shoichi

Arisawa, general manager of the investment research department

at IwaiCosmo Securities.

"The market was dragged lower by a lack of corporate buying

of their own stocks at the end of the fiscal half."

Corporate share buybacks this year are at record levels in

Japan as domestic firms moved to boost investor returns on the

back of corporate governance reform, helping the Nikkei and the

Topix to hit their peaks.

The market is also cautious ahead of the release of the

crucial U.S. jobs report later this week and the outcome of the

Liberal Democratic Party's leadership election on Saturday, said

Arisawa.

Chip-testing equipment maker Advantest ( ADTTF ) fell 1.39%

and technology start-up investor SoftBank Group lost

1.65%. Uniqlo-brand owner Fast Retailing ( FRCOF ) slipped 0.64%.

Energy explorers lost 3.4% to become the worst

performer on the Tokyo Stock Exchange's 33 industry sub-indexes.

On the other hand, the insurance sector gained

0.78% to become the top-performing industry index.

Infrastructure services provider Ebara ( EBCOF ) jumped 5.7%

to become the top percentage gainer on the Nikkei.

Drug maker Sumitomo Pharma ( DNPUF ) gained 3.7%.

Of more than 1,600 stocks trading on the TSE's prime

section, 24% rose and 71% fell, and 3% traded flat.