* Japan No.5 bank to buy Citi asset firm for $1.1 bln -paper
* Sumitomo Trust may sell stake in Nikko Asset to SMFG -paper
* Sumitomo Trust will also consider IPO of unit -paper
TOKYO, July 29 (Reuters) - 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.
Sumitomo Trust, Japan's fifth-largest bank, is likely to make the acquisition by October, the paper said, without identifying its sources.
Acquiring Nikko Asset's roughly 9 trillion yen in assets under management would make Sumitomo Trust Japan's top asset manager with a total of about 35 trillion yen, the Nikkei said.
Nikko Asset is Japan's third-largest mutual fund manager, and is well known to both institutional and retail investors.
Spokesmen for both Nikko Asset and Sumitomo Trust declined to comment, as did a Hong Kong-based spokesman for Citigroup.
Sumitomo Trust may consider selling a stake in Nikko Asset to Sumitomo Mitsui Financial Group, Japan's third-largest bank, the paper said.
Sumitomo Mitsui recently acquired Citigroup's Japanese retail brokerage, Nikko Cordial.
Sumitomo Trust will also consider taking Nikko Asset public, the paper said.
Citigroup has been selling off its assets in the world's second-largest economy after taking $45 billion in U.S. government money following the credit crisis. (Reporting by David Dolan; Editing by Edwina Gibbs)