Over $6 billion was wiped off global cryptocurrency markets in a day, led by XRP and ethereum as prices of digital coins continued to fall. The entire market capitalization or value of cryptocurrencies had plunged $6.72 billion in 24 hours as of about 11:32 a.m. HK/SIN time on Friday, according to data from Coinmarketcap.com. That came after a sharp sell-off across the board on Thursday, which erased billions of dollars of value in a matter of hours. Friday's drop was led by XRP, which was trading at around 39.13 cents at 11.32 a.m. HK/SIN time, marking a 7.9 percent drop from the day before. It fell as low as 37.89 cents. Ethereum also fell to around $191.07, dropping 7.4 percent from the day before. Meanwhile, bitcoin largely stabilized at around $6,278.61, falling just under 0.8 percent on the day. Ethereum, bitcoin and XRP pared some of those losses, but were still sharply lower.

It's not clear there was a catalyst that sparked the selling over Thursday and Friday, but financial markets around the world saw big declines. There's also been a lot of negative sentiment toward cryptocurrencies from important financial institutions and major figures. "Continued rapid growth of crypto assets could create new vulnerabilities in the international financial system," the International Monetary Fund said in a recent report. Nouriel Roubini, an economist who predicted the 2008 financial crisis and a long-time cryptocurrency bear, sounded a fresh warning about digital coins. "Crypto is the mother or father of all scams and bubbles," Roubini told the U.S. Senate Committee on Banking, Housing and Community Affairs at a hearing on Thursday.