UNITED NATIONS, Aug. 10 (Xinhua) -- The UN Conference on Trade and Development (UNCTAD) called for actions to curb cryptocurrencies in developing countries in three policy briefs published on Wednesday. While private digital currencies have rewarded some, and facilitate remittances, they are an unstable financial asset that can also bring social risks and costs, the UN trade and development body warned. The three newly-released UNCTAD policy briefs examined the risks and costs of cryptocurrencies, including the threats cryptocurrencies bring to financial stability, domestic resource mobilization and the security of monetary systems. Global use of cryptocurrencies has increased exponentially during the...