Key Indian cities re-opened for business on Monday, with long queues for buses in the financial hub of Mumbai while traffic returned to the roads of New Delhi after a devastating second wave of coronavirus that killed hundreds of thousands.

The 100,636 new infections of the past 24 hours were the lowest in the world's second-most populous nation since April 6, and well off last month's peaks of more than 400,000, allowing authorities to re-open parts of the economy.

"We have to save...