SAO PAULO, March 26 (Reuters) - Brazil's central bank called an auction on Friday to buy U.S. dollars on the spot foreign exchange market as part of an ongoing effort to boost international reserves and limit currency market volatility.

Brazil's currency, the real (BRBY), was trading 0.83 percent weaker at 1.825 per dollar shortly after the announcement. (Reporting by Silvio Cascione; Writing by Peter Murphy)