Facebook's hopes of launching a new virtual currency have suffered another blow, as two more financial regulators said on Tuesday they are paying close attention to the social media company's plans.

Both the international Financial Stability Board and the UK's Financial Conduct Authority have said they will not allow the world's largest social network to launch its planned digital currency without close scrutiny.

Facebook is hoping to upend the global payments market with its new currency, called Libra, which the company promises will be instantaneous and almost free. The company is working with other internet and payments groups, including Uber,