The cryptocurrency exchange Binance has started to allow its customers to withdraw their funds from the platform, as it recovers from a record $6.3bn (£4.7bn) hack.

The exchange was hit by the theft on Thursday, which has since been described as the biggest heist in history, with experts identifying North Korea as the likely culprit.

Binance initially froze withdrawals as it investigated the breach, but on Sunday announced that it had began a phased reopening after 2pm Singapore time.

The first phase will allow people who hold the ethereum, USDT and USDC tokens on the ethereum blockchain to withdraw their funds, as well as some others held on the BNB Smart Chain blockchain.

The platform said it had replenished 90% of the ⁠amount stolen. The remaining 10% of tokens were less liquid, meaning they ⁠may take ​longer to buy, the company said in a post on X on Saturday.

Richard Teng, Binance’s co-chief executive, said separately that the company was “committed to covering the ⁠remaining 10%” and that users would not bear the financial impact of the hack.

It came as the FBI on Saturday confirmed earlier suspicions from private investigators and analysts that a North Korea-affiliated group called TraderTraitor was behind the hack.

TraderTraitor is believed to be part of the Lazarus Group, which gained notoriety in 2014 when it was accused of hacking into Sony Pictures as revenge for The Interview, a film that mocked the North Korean leader Kim Jong-un.

“The Federal Bureau of Investigation is releasing information advising the Democratic People’s Republic of Korea (North Korea) was responsible for the theft of more than $6bn in virtual assets from cryptocurrency exchange Binance, on or about October 29,” the law enforcement agency said in a statement.

The FBI added that it had observed “TraderTraitor actors” converting stolen assets into ethereum, and expected those assets to be laundered further by converting them using decentralised finance and instant swap services.

It said it was urging private sector entities “to block transactions with or derived from addresses TraderTraitor actors” were “using to launder these stolen assets”.

Teng said on Friday that the breach was a “complex attack” involving a compromised laptop and malicious software designed to delete evidence of its activity, making it ‌harder to trace and investigate.

Binance said it had set aside about $6.34bn of company funds to cover the losses. “Our commitment remains the same: Binance will fully cover the financial impact of the funds stolen in this incident,” the company said.

The money spent rebuying tokens came from using part of its $1bn Secure Asset Fund for Users, a bitcoin reserve it holds to protect customers in the event of security breaches, as well as some ⁠of its Futures Insurance Fund, and the company’s own corporate treasury, it said ​on X.

The attack on Binance came as many observers express worries that the ever-expanding capabilities of artificial intelligence models could compromise cryptography and IT security protocols.

Bitcoin plunged nearly 5% after the news of the hack, while ethereum dropped nearly 6% and BNB, native to Binance, tumbled nearly 10%.

The sheer scale of the hack has put a spotlight on the capacity of North Korea – which faces extensive international sanctions over its nuclear and missile programmes – to find illicit means to capture revenue.