Buying into initial coin offerings (ICOs) can lead to the total loss of an investment, said the head of a top European regulator.

ICOs bear similarities to initial public offerings for a stock, but in an IPO, the investor usually has a stake in the company, whereas coin sales differ widely in terms of acquired rights. That's been a primary criticism of ICOs, but differences in regulation are also important factors for investors to consider, according to Steven Maijoor, the chair of the European Securities and Markets Authority.

"You don't have the regular protection that regulated investments offer, and can lose all of your investments," Maijoor said Tuesday. "As a European securities market authority, we have warned, in November, about the so-called ICOs because while ICOs in principle can give you services in return for the coin that you buy, or a share in the revenue, this happens in a very unregulated space."