MADRID - Mass crypto-asset advertising campaigns in Spain will require an authorisation from the stock market supervisor CNMV, the government said on Monday in its official bulletin.

Advertisers and companies that market crypto-assets will have to inform the watchdog at least 10 days in advance about the content of campaigns targeting more than 100,000 people.

The new regulations will start from mid-February, allowing the CNMV to specifically monitor advertising for all types of crypto-assets and to include warnings about risks involved in such investment.

Cryptocurrencies such as Bitcoin have experienced high price volatility accompanied by a significant increase in aggressive advertising to attract investors.

Central bankers around the world are worried about the rise of cryptocurrencies, especially stablecoins, which derive their value from one or more official currencies. They fear that could dent their control over payments, banking and, ultimately, the supply of money.

(Reporting by Jes?s Aguado, editing by Andrei Khalip and Ed Osmond)