* Sells shares to foreign investors - traders
* Bamburi left with 3 percent in rival Athi River
* Bamburi shares flat, Athi River down 0.5 percent
(Adds quote, details, background)
NAIROBI, Oct 21 (Reuters) - Bamburi Cement, Kenya's largest cement company, sold an 11 percent stake in rival Athi River Mining, traders said on Wednesday, reducing its holding from 14 percent.
Bamburi, which is majority owned by France's Lafarge, sold 10 million shares at the Nairobi Stock Exchange (NSE) during Monday's session, the NSE said.
"Athi River Mining was the day's main feature with 10 million shares," NSE said in its market report.
NSE said the industrial and allied shares sector under which Athi River is listed, moved 11.8 million shares during Monday's session, accounting for 54 percent of the day's traded volume at the bourse.
"Bamburi has sold its shareholding in Athi River Mining and some foreign investors have bought the shares," a market source, who did not wish to be named, said.
Bamburi was not immediately available to comment.
The company's stock price was unchanged at 160 shillings ($2.13) at the close of trading on Wednesday. Athi River shares were down 0.5 percent.
Bamburi is the largest cement firm in Kenya while Athi River is ranked third after Portland Cement. (Reporting by Duncan Miriri; Editing by Erica Billingham)