TOKYO - Labor union members at Japanese department store operator Sogo & Seibu Co. went on strike at its flagship Tokyo store Thursday in a rare work stoppage amid job security concerns stemming from the parent company's plan to sell the chain to a U.S. fund.

Despite the first strike by a major department store union in 61 years amid an intensifying labor dispute, the parent Seven & i Holdings Co. said it decided at an extraordinary meeting the same day to sell the struggling department store chain to Fortress Investment Group LLC on Friday.

Some 900 workers staged a walkout from the Seibu Ikebukuro store, while 300 people held a protest rally at a nearby park joined by members from labor unions of other department stores.