SEOUL — One of the largest cryptocurrency exchanges suspended operations Wednesday after announcing hackers stole more than $31 million worth of virtual currency, pushing down the value of some top names, including bitcoin.

The attack on the South Korea-based exchange, Bithumb, was smaller in value than some of the biggest hacks on cryptocurrencies. But it underscored the potential vulnerabilities for web-based trading and sent ripples across many cryptocurrency networks.

A statement from Bithumb gave no details on how hackers penetrated the system, which is among the top sites for cryptocurrency trading. Bithumb said its cryptocurrency holdings were shifted to an offline “cold wallet,” and any losses for traders would be covered.

Deposit and withdrawal services were halted “for the time being,” the exchange said. It did not say when they could resume.

News of the breach sent Bitcoin’s price down sharply, but the value later leveled off.