Hundreds of millions of people in India, including in its two largest cities, have been ordered to wear face masks or coverings amid a nationwide lockdown to combat the spread of the coronavirus pandemic.

Residents in the capital New Delhi and Mumbai, which have a combined population of almost 40 million, as well as in the most populous state Uttar Pradesh where 200 million live, will have to cover their faces in public spaces.

“Wearing of facial masks can reduce the spread of coronavirus substantially,” Delhi Chief Minister Arvind Kejriwal said late Wednesday. “Therefore, it has been decided that facial masks will be compulsory for anyone stepping out of their house.”