Bitcoin is showing no signs of slowing down, blowing past $US9,000 less than a week after topping $US8,000 and now quickly closing in on five big figures.

The price of the largest cryptocurrency by market value is soaring as it gains greater mainstream attention despite warnings of a bubble in what not everyone agrees is an asset. From Wall Street executives to venture capitalists, observers have been weighing in, with some more skeptical than others. Bitcoin has climbed more than 40 per cent over the past two weeks.

"Bitcoin has seen another frenzy of buying as the fear of missing out trade bites even harder," analysts at IG Group, a trading-platform operator, wrote in a note on Monday. "There are others who see downside risks from the introduction of bitcoin futures," they wrote.

The rapid appreciation of Bitcoin has made it difficult for bullish analysts and investors to keep their predictions up to date. Bitcoin.com

The surge has swept along individual investors. The number of accounts at Coinbase, one of the largest platforms for trading bitcoin and rival ethereum, has almost tripled to 13 million in the past year, according to Bespoke Investment Group.

Bitcoin climbed as high as a record $9,720.95 on Monday, and was recently up about 16 per cent compared with trading late on Friday.