"It is not allowed for people and businesspeople to use foreign currencies in buying and selling goods and services in the local market," said the deputy finance minister Janet Mbene in Arusha, northern Tanzania.

"We are studying the trend and we'll talk to the business community involved in such businesses and encourage them to start using our Tanzanian shilling instead of the U.S. dollar in their transactions," she was quoted by the Guardian newspaper as saying.

The official when opening a two-day seminar on financial markets and financial institutions said transaction in foreign currencies in local market contributed to the devaluation of the Tanzanian shilling against major international currencies.