NEW DELHI/MUMBAI (Reuters) - India will propose a law banning cryptocurrencies, fining anyone trading in the country or even holding such digital assets, a senior government official told Reuters in a potential blow to millions of investors piling into the red-hot asset class.

The bill, one of the world's strictest policies against cryptocurrencies, would criminalise possession, issuance, mining, trading and transferring crypto-assets, said the official, who has direct knowledge of the plan.

The measure is in line with a January government agenda that called for banning private virtual currencies such as bitcoin while building a framework for an official digital currency. But recent government comments had raised investors' hopes that the authorities might go easier on the booming market.