San Francisco, Nov 13 (IANS): Beleaguered crypto exchange FTX on Sunday admitted that "unauthorised transactions" have drained hundreds of millions of dollars from its wallets, saying the company has moved many digital assets to a new "cold wallet custodian".

FTX, which last week filed for bankruptcy in the US, did not reveal how much it lost in unauthorised transactions but reports claimed the amount could be as high as $600 million.

"We are in the process of removing trading and withdrawal functionality and moving as many digital assets as can be identified to a new cold wallet custodian. As widely reported, unauthorised access to certain assets has occurred," Ryne Miller, the general counsel at FTX US, said in a tweet.

He added that an active fact review and mitigation exercise was initiated immediately in response.

"We have been in contact with, and are coordinating with law enforcement and relevant regulators," Miller said.

FTX on Friday filed for Chapter 11 bankruptcy in the US, as its Founder and CEO Sam Bankman-Fried resigned from his role.

John J Ray III has been appointed the new CEO and nearly 130 additional affiliated companies -- including FTX US and Alameda Research -- have also begun the bankruptcy process.

Earlier, world's largest crypto exchange Binance took a U-turn on acquiring FTX, saying it was backing out of the deal after reviewing the company's finances, leading to further fall in major cryptocurrencies.

Binance had signed a non-binding, letter of intent to purchase FTX for an undisclosed sum.

FTX has fallen from being the third largest crypto exchange to 62nd, according to CoinMarketCap.