London police have seized a trove of cryptocurrency worth £114 million ($159,000) that criminals were planning to launder, the UK's largest-ever seizure of digital currency.

The Metropolitan Police said late Thursday that detectives had seized the digital currency after receiving information about the transfer of criminal assets. 

The statement did not say what type of cryptocurrency was involved.

"As technology and online platforms develop, some are moving to more sophisticated methods of laundering their profits", said deputy assistant commissioner Graham McNulty.

"But we have highly trained officers and specialist units working day and night to remain one step ahead," McNulty added.

It was "the largest cryptocurrency seizure in the UK and believed to be one of the largest globally," the police force said. 

Cryptocurrencies cannot be traced by a country's central bank, making them difficult to regulate.

Bitcoin, the world's most popular virtual unit, was created in 2008 as an alternative to traditional currencies.

Cryptocurrencies are minted by solving puzzles using powerful computers that consume enormous amounts of electricity.

Bitcoin fell below $30,000 on Tuesday for the first time since January, down from its high of $64,870 reached in April.