Sumitomo Trust and Banking Co has agreed to buy Citigroup's Japanese asset manager, Nikko Asset Management, for about 100 billion yen ($1.1 billion), the Nikkei newspaper said on Wednesday.

The acquisition by Sumitomo Trust, Japan's fifth-largest bank, is likely to take place by October, the paper said, without identifying its sources.

Sumitomo Trust will also consider taking Nikko Asset public, the paper said.

(Reporting by David Dolan)