LONDON (Reuters) - The amount of cryptocurrency stolen in hacks globally more than doubled in the first six months of 2024 from a year earlier, driven by a small number of large attacks and rising crypto prices, blockchain researchers TRM Labs said on Friday.

Hackers had stolen more than $1.38 billion worth of crypto by June 24, 2024, compared with $657 million in the same period in 2023, TRM Labs said in a report.

The median theft was one-and-a-half times larger than the year before, the report said.

"While we have not seen any fundamental changes in the security of the cryptocurrency ecosystem, we have seen a significant increase in the value of various tokens - from bitcoin to ETH (ether) and Solana - compared to the same time last year," said Ari Redbord, global head of policy at TRM Labs.

This means that cybercriminals are more motivated to attack crypto services, and can steal more when they do, Redbord said.

Crypto prices have generally recovered from the lows hit in late 2022 in the aftermath of the collapse of Sam Bankman-Fried's crypto exchange, FTX. Bitcoin hit an all-time high of $73,803.25 in March this year.

Among the largest crypto losses so far this year was the roughly $308 million worth of bitcoin stolen from Japanese crypto exchange DMM Bitcoin, in what the company called an "unauthorised leak".

Cryptocurrency companies are frequent targets for hacks and cyberattacks, although losses of this scale are rare.

Stolen cryptocurrency volumes in 2022 were around $900 million, Redbord said, partly due to the more than $600 million stolen from a blockchain network linked to the online game Axie Infinity. The United States has linked North Korean hackers to that theft.

The United Nations has accused North Korea of using cyber attacks to help fund its nuclear and missile programs. North Korea has previously denied allegations of hacking and other cyberattacks.

(Reporting by Elizabeth Howcroft; Editing by Tommy Reggiori Wilkes and Kim Coghill)