A hacker has stolen cryptocurrencies worth around $615m from Ronin, a Blockchain platform behind popular non-fungible token (NFT) game Axie Infinity, in one of the largest decentralised finance (DeFi) breaches to date. 

The Blockchain platform and Axie Infinity operator Sky Mavis admitted the security breach, saying that 173,600 Ethereum and 25.5M USDC (a cryptocurrency pegged to the US dollar) were drained from the Ronin bridge in two transactions.

The cryptocurrencies would have been worth about $615m.

In a blog statement on 29 March Ronin said: "We are working with law enforcement officials, forensic cryptographers, and our investors to make sure all funds are recovered or reimbursed. All of the AXS, RON, and SLP on Ronin are safe right now.

"There has been a security breach on the Ronin Network. Earlier today, we discovered that on March 23rd, Sky Mavis's Ronin validator nodes and Axie DAO validator nodes were compromised resulting in 173,600 Ethereum and 25.5M USDC drained from the Ronin bridge in two transactions (1 and 2). 

"The attacker used hacked private keys in order to forge fake withdrawals. We discovered the attack this morning after a report from a user being unable to withdraw 5k ETH from the bridge."

It added: "We moved swiftly to address the incident once it became known and we are actively taking steps to guard against future attacks. To prevent further short term damage, we have increased the validator threshold from five to eight."