Investors have pulled $3.6bn (£2.7bn) in funds from the cryptocurrency exchange Binance as it recovers from a record hack in which billions were stolen from customer accounts.

The platform was hit by a $6.3bn theft on Thursday, which has since been described as the biggest heist in history. Experts identified North Korea as the probable culprit.

Binance initially froze withdrawals as it investigated the breach but on Sunday announced it had begun a phased reopening.

By Sunday afternoon, the platform had processed $4.6bn in withdrawals and $1bn in deposits, resulting in a net outflow of about $3.6bn – representing 2.1% of its $171bn in total assets under management.

The numbers were confirmed by the company in its latest proof of reserves snapshot. A full report is expected on Monday.

Binance said: “After an initial spike, withdrawal volumes have declined and are stabilising as expected, while deposit volumes have remained substantial.”

The crypto exchange told its customers that market conditions were stable and that its team was “testing rigorously the remaining networks and assets”.

“We know how important safe and reliable access to your funds is and will share details of the next phase as soon as we can,” it said on X.

In the first phase Binance restored withdrawals for 15 networks and assets, including ethereum, USDT and USDC tokens on the ethereum blockchain, as well as some others held on the BNB Smart Chain blockchain. Later on Sunday, dealing in the Dogecoin and Avalanche currencies resumed on their own platforms.

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 users would not bear the financial impact of the hack.

On Saturday the FBI 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.

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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 own corporate treasury, Binance said ​on X.

The hack came as many observers expressed 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.