By Jemima Kelly LONDON (Reuters) – Web-based digital currency bitcoin hit its highest levels in almost three years on Friday, extending gains since India sparked a cash shortage by removing high-denomination bank notes from circulation a month ago. Indian prime minister Narendra Modi announced a shock move on Nov. 8 to ditch 500 and 1,000 rupee notes – worth a combined $256 billion – that he said were fuelling corruption, being forged and even paying for attacks by militants who target India.