Indian Prime Minister Narendra Modi on Tuesday announced that 500 and 1,000 rupee banknotes would be withdrawn from circulation at midnight, saying it was part of a crackdown on rampant corruption and counterfeit currency.The surprise step appears designed to bring billions of dollars worth of cash in unaccounted wealth into the mainstream economy, as well as hit the finances of Islamist militants who target India and are suspected of using fake 500 rupee notes to fund operations.“Black money and corruption are the biggest obstacles in eradicating poverty,” Modi said in an address to the nation.New 500 and 2,000 rupee denomination notes will be issued at a later date, he added.