The notice seen by Sapo Angola also directs that all foreign currency deposits should be made with a bank domiciled in the country.
BNA said the purchase and sale of diamonds by Angola-based companies and individuals will be made in the local currency, Kwanza.
However, the bank also gave the local diamond buyers and sellers to trade in foreign currency if both parties agree to do so.
BNA opened the foreign currency trading platform (FXGO) to diamond companies last month.
The FXGO platform, which was contracted to Bloomberg, had since end of March been utilised by 23 banks as well as eight companies in the oil sector.
Apart from diamond companies, BNA also wants the national treasury and large companies with foreign currency purchase needs, such as air navigation companies, to access the FXGO platform.
The FXGO platform allows real-time trading between foreign currency sellers and buyers, with exchange rates freely negotiated between the parties.
Mathew Nyaungwa, Editor in Chief of the African Bureau, Rough&Polished