South Korean cryptocurrency exchange Youbit said on Tuesday that it is shutting down after attacks by hackers caused losses worth 17 percent of its total assets.

Youbit said on its website that it had been hacked at 4.35am local time, without revealing the value of the cryptocurrencies that it lost.

"To minimize the damages of our customers, we will allow them to withdraw about 75 percent of the balance," the statement said according to South Korean news agency Yonhap.

The remaining crypto assets were not at risk because they were stored in a "cold wallet," a way of storing cryptocurrencies offline, for example in a USB drive or in other physical forms.

YouBit, which was formerly known as "Yapizon," had faced another cyberattack in April, when hackers stole 5.5 billion won (US$5.06 million) worth of cryptocurrencies, according to local media.

Cryptocurrencies have become a popular form of payment and a thriving investment asset in Japan and South Korea, two of the largest markets for cryptocurrencies in the world, despite the latter facing cyberattacks on several occasions.

The latest attack took place only days after South Korean intelligence authorities said that North Korea was behind the cyberattacks on cryptocurrency exchanges in the South.