An online marketplace OpenSea says it is now worth $13.3bn (£9.8bn) following a new investment of $300m.

The platform enables trade in NFTs (non-fungible tokens), unique pieces of digital code that can be associated with a digital asset such as a work of digital art.

Some NFTs have sold for millions of dollars.

OpenSea says trades on the platform rose 600-fold last year, but some critics say the valuation is too high.

“In 2021, we saw the world awaken to the idea that NFTs represent the basic building blocks for brand new peer-to-peer economies,” wrote Devin Finzer, who co-founded the company in 2017,

But others argue the spiralling valuations of some crypto-businesses reflects a shortage of places for investors to put their money.