The withdrawal of 500- and 1,000-rupee banknotes from circulation is a drastic measure to crack down on rampant corruption and counterfeit currency.

About a quarter of the US$2 trillion (S$2.8 trillion) economy is unaccounted for, Bloom- berg reported yesterday.

It will be a vast exercise because the notes constitute 84 per cent in value of all Indian banknotes in circulation.

Mr Narendra Modi came to power in 2014 promising to clean up corruption and curb the generation of "black money", or unaccounted money, that forms part of India's shadow economy.