The company said that sales dived by a quarter in June as it was still weighed down by the impact of the pandemic and lockdowns in key regions.
The retailer reopened hundreds of its UK stores last month after the Government gave non-essential retailers the green light to welcome customers again.
However, the company has not confirmed how many of these closures could affect its 300 UK stores.
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Weekday, Monki, COS and other brands within the Swedish fashion group are also expected to be affected by the closure plans.
H&M said in its second quarter report to investors that it increased its previous closure plans by around 40 after feeling the impact of the virus across Europe.
The group also intends to open 130 new stores elsewhere during the current year.
At the end of June, H&M said that 350 of its stores, representing 7% of all sites, were still closed as a result of the pandemic.
Helena Helmersson, chief executive officer of the group, said: "I am full of admiration for our employees' commitment, drive and perseverance during this very challenging time.
"As we have reopened our stores, sales have begun to recover at a faster rate than expected.
"To meet the rapid changes in customer behaviour caused by Covid-19 we are accelerating our digital development, optimising the store portfolio and further integrating the channels.
"With our ambitious sustainability work we want to continue to lead fashion retail towards a more sustainable future."