Seoul-based bitcoin exchange Bithumb said Wednesday it had lost over $30 million as the result of being hacked, the second cyberattack in two weeks to hit a major South Korean cryptocurrency exchange as safety concerns hamper the industry and weigh on prices.

Bithumb said it had lost $31.56 million (35 billion won) worth of cryptocurrencies and has temporarily halted withdrawal and deposit services. The company said it would compensate customers for all lost assets.

Bitcoin...