Leading Japanese cryptocurrency exchange Liquid has been hit by hackers, with almost $100m (£73m) estimated to have been stolen.

The company announced that some of its digital currency wallets have been "compromised."

It is the second major theft of cryptocurrencies to take place in recent days.

Last week, digital token platform Poly Network was at the centre of a $600m heist.

"We are sorry to announce that #LiquidGlobal warm wallets were compromised, we are moving assets into the cold wallet," the company said on Twitter.

So-called 'warm' or 'hot' digital wallets are usually based online and designed to allow users to access their cryptocurrencies more easily, while 'cold' wallets are offline and harder to access and therefore usually more secure.

Blockchain analytics firm Elliptic said its analysis showed that around $97m in cryptocurrencies had been taken, with Bitcoin and Ethereum tokens amongst the haul.

Liquid has said that it was tracing the movement of the stolen cryptocurrencies and working with other exchanges to freeze and recover the assets.

Founded in 2014, Liquid operates in over 100 countries and serves millions of customers around the world.

It is one of the world's top 20 biggest cryptocurrency exchanges by daily trading volumes, according to CoinMarketCap data.

Last week, $600m was stolen from blockchain site Poly Network after a hacker exploited a vulnerability in its system.

"The amount of money you have hacked is one of the biggest in defi [decentralised finance] history," Poly Network said.

Since then the hacker, who goes under the name of Mr White Hat, has returned around $427m of the assets.

Liquid is not the only Japanese cryptocurrency platform to be hit by a major heist.

In 2014, Tokyo-based exchange MtGox collapsed after almost half a billion dollars of bitcoin went missing, while Coincheck was hacked in a $530m heist in 2018.