UPDATE 1-Mexico's Femsa seeks to sell a 5 pct stake in Heineken

(Adds details on Femsa stake, stock prices)

MEXICO CITY, Sept 18 (Reuters) - Heineken Holding NV shareholder Fomento Economico Mexicano (Femsa) said on Monday it was planning to sell an approximate 5 percent stake in the Dutch brewery, worth 2.5 billion euros ($3 billion).

Femsa, a Mexican bottler and retailer, said the offer would be aimed at institutional investors outside of Mexico.

Femsa holds 12.53 percent of Heineken, or roughly 72 million shares, according to Thomson Reuters data. That would mean Femsa is selling about 40 percent of its stake.

The Mexican company said it would retain Heineken board seats after the offer closes. It did not give any further details on the share offer.

In July, Heineken told Femsa's bottling unit Coca-Cola Femsa that it was set to lose its contract to distribute the beer in Brazil. At the time, Femsa executives said talks about dissolving that contract would not affect the larger strategic relationship between the companies.

Shares in Femsa at 1238 local time (1738 GMT) on Monday were up about 1.5 percent at 174.69 pesos ($9.84) per share, while Heineken shares were down 0.06 percent at 87.59 euros per share.

($1 = 17.7460 pesos) ($1 = 0.8380 euros) (Reporting by Gabriel Stargardter; Editing by Christian Plumb and Rosalba O'Brien)