Last month the government launched Sango Coin amid a sharp fall in Bitcoin prices and doubts over the project's viability in a country with poor internet connection and destabilised by conflict.

Sales of the initial $21m (£17m) on offer have been slow, with just over 5% of the target bought in the hours after its launch on 21 July.

According to the Sango website, foreign investors could obtain citizenship for $60,000 worth of crypto - with the equivalent Sango Coins held as collateral for five years - and "e-residency" for $6,000, held for three years.

Investors would also be able to by a 250 sq m plot of land for $10,000, with the Sango Coins locked away for a decade.

The constitutional court ruled that nationality did not have a market value and that residency required a physical stay in the country.

A government spokesman had no response on Monday and the impact of the ruling on ambitious crypto project is not clear, Reuters news agency reports.