Bitcoin surged back above $US4,000 overnight and kept climbing, a short time ago trading at more than $US4,200.

There were smaller gains for Bitcoin Cash, while Ethereum, the second-largest cryptocurrency by market cap, also saw renewed demand. It’s back above $US300 for the first time in two weeks.

Bitcoin has been rising steadily in recent days — it kicked off the week with a push towards $US4,000 in a more risk-off environment, as the market responded to more tensions between the US and North Korea.

Here's the price action this week:

Amid the latest Bitcoin rally, Coindesk reported overnight that Bitcoin developers may be preparing for a second split in the currency, following the split at the start of August that created Bitcoin Cash.

The next “hard fork” will lead to the establishment of Bitcoin Gold, as developers work on improving protocols to increase transactions speeds.

Morgan Stanley’s Australian CEO James Gorman also weighed into the Bitcoin debate overnight, saying that the cryptocurrency is “more than just a fad“.

That’s certainly a friendlier tone than the tone adopted by JP Morgan CEO Jamie Dimon, who’s launched repeated attacks against Bitcoin calling it a “fraud“.