Bitcoin hit a low of $6,915.55 late Thursday afternoon, its lowest since Feb. 6, according to CoinDesk's bitcoin price index. That marked a decline of nearly 29 percent for the week and 50 percent for the year so far. Bitcoin had recovered above $7,000 as of 6 p.m. ET.
The largest digital currency by market capitalization fell more than 9 percent to below $7,200, according to CoinDesk's bitcoin price index. That brought the quarter-to-date decline to 48 percent.
Ethereum, the second-largest cryptocurrency by market cap, declined 11 percent to near $397, its lowest since Nov. 23, according to CoinMarketCap. At that price, ethereum was down roughly 29 percent for the week and nearly 47.5 percent for the quarter.
Bitcoin three-month performance
Some analysts have expected selling in bitcoin and other cryptocurrencies to pick up toward the mid-April deadline to file U.S. taxes as first-time investors realize they need cash to pay capital gains tax.
After a massive run higher in 2017, cryptocurrencies have fallen sharply to start the year due to regulatory uncertainty. South Korean, Japanese and U.S. authorities have stepped up their scrutiny of cryptocurrency trading in the last few months.
The total value of all cryptocurrencies tracked by CoinMarketCap has fallen by about $550 billion from a high of more than $830 billion in early January.
The latest decline in bitcoin also came as U.S. stocks tried to recoup some of the month's losses.
The S&P 500 fell more than 2.5 percent for the month following worries about a trade war and a sharp drop in Facebook shares on a data scandal involving 50 million accounts.
"People are sitting on massive profits on almost every asset class for the last 10 years. Crypto happened to represent the culmination of that excitement and exuberance about tech," said Benjamin Roberts, co-founder and CEO of Citizen Hex, an ethereum-focused start-up backed by three Canadian venture funds.
Information technology lost 3.95 percent in March as the third-worst-performing sector in the S&P 500. Tech stocks led market gains Thursday.