Sumitomo Trust & Banking Co. said Friday it will invest more than 40 billion yen in Yachiyo Bank to help the Tokyo-based regional bank repay 35 billion yen in public funds to the government.

Sumitomo Trust said that under the capital and business tieup, it will buy all of Yachiyo's 35,000 preferred shares, worth about 40 billion yen, which Yachiyo issued to the government when it received the funds.

The major trust bank will also purchase Yachiyo common stock equivalent to about 5 percent of the regional bank's outstanding shares. The value of the purchase has yet to be determined but it is estimated at several billion of, yen Sumitomo Trust said.

Yachiyo will also purchase some 500 million yen worth of Sumitomo Trust shares on the open market.