The bank sold 7,400 of the 70,000 contracts on offer, with 2,200 contracts maturing on Nov. 1 and 5,200 maturing on Dec. 1.

The bank sold $1.78 billion in reverse swaps in another offering earlier on Friday. The action is akin to a purchase of dollars by the central bank in futures markets.

Brazil's currency, the real, was trading 0.27 percent stronger at 2.0120 reais per US dollar shortly after the auction.