The labor union of the Sogo & Seibu department store chain has staged a one-day strike. The flagship store in Tokyo's Ikebukuro district was shut down on Thursday.

The strike is in response to the planned sale of the struggling department store. Sogo & Seibu's parent company Seven & i Holdings decided in November to sell it to US-based firm Fortress Investment Group.

The labor union's objection stems from worries about job losses. The strike is the first at a major department store in Japan in about 60 years.

Seven & i held a board meeting earlier in the day and approved a sale worth 220 billion yen, or 1.5 billion dollars. It plans to complete the deal on Friday.

Fortress Investment's Japanese unit says the firm will do its best to keep Sogo & Seibu's department store business going. It also says it will work with Seven & i to preserve as many jobs as possible.

But talks with the union have yet to lead to a breakthrough.

The strike comes as the business environment is worsening for department stores. Seven & i merged with Millennium Retailing, the predecessor of Sogo & Seibu, in 2006. The company believed the move would improve its overall competitiveness. It thought the brand recognition of the department stores would complement the new products developed by its convenience stores.

But the department store industry began to struggle soon after, as specialty shops and online retailers gained popularity. Sogo & Seibu has logged net losses in 10 out of the 17 years since the merger, including four straight years through fiscal 2022.