Following the sale, Showa Denko, a chemical engineering group, buy the rest of Hitachi Chemical's outstanding shares through a tender offer, the newspaper said.

Showa Denko said in a statement it was considering various options to boost its corporate value including the purchase of shares in Hitachi Chemical but that nothing had been decided.

Officials at Hitachi and Hitachi Chemical said the report was not based on anything they had announced.

Hitachi Chemical shares soared 16% in price in morning Tokyo trade while those of Hitachi climbed more than 3%. Showa Denko shares fell as much as 8.7%.

Hitachi last month narrowed suitors for the chemical unit to a handful of bidders including Nitto Denko Corp and U.S. buyout funds Bain Capital LP and Carlyle Group LP.

Hitachi has been among the most aggressive of Japan's conglomerates in reorganising its business, selling non-core assets while buying foreign businesses to expand overseas.

Other divestiture includes chip-making equipment manufacturer Hitachi Kokusai Electric and power tool unit Hitachi Koki.

Hitachi Chemical makes materials for semiconductors, displays and lithium-ion batteries.

(Reporting by Arunima Kumar in Bengaluru and Junko Fujita in Tokyo; Editing by Maju Samuel and Christopher Cushing)