Source: iStock/D-Keine

At approximately 1:00am June 27 (GMT+8), a hacker accessed the personal funds of about 90 Bitrue users and stole XRP 9.3 million (USD 4 million) and ADA 2.5 million (USD 227,900), the Singaporean crypto exchange said.

"First of all, please let us assure you that this situation is under control, 100% of lost funds will be returned to users, and we are reviewing our security measures and policies to ensure this does not happen again," the company said, adding that the stolen funds will be returned to affected users "as soon as possible."

The exchange hopes to re enable trading functionality in the coming hours (08:29 UTC).

"Withdrawals will be offline for a slightly longer period while we continue investigating the situation," it added.

The company has also "contacted the relevant authorities in Singapore" for help, while Huobi, Bittrex and ChangeNOW exchanges have already frozen "the affected funds and accounts."

The exchange is ranked 67th by trading volume, according to coinpaprika.com. The 24 hours trading volume on the exchange stands at USD 77 million.