Same store sales at Uniqlo's stores in Japan rose 3.9% in June, after warm weather boosted sales of summer garments.

Fast Retailing Co, which operates the clothing chain, said sales were also helped by the government's 'Super Cool Biz' initiative which encourages workers to dress more casually to help reduce the use of air conditioners to save electricity.

Earlier this month the company launched a new range of lightweight clothing in support of this campaign. Items included polo shirts with deodorising capabilities, and a bra top garment with a built-in bra to help to cut down on the number of layers worn.

In June, total Uniqlo sales including online sales increased by 9.4%, the company said.