Stockholm’s OMX 30 index fell eight percent in five minutes at the start of trading before recovering most of the losses.
Markets in Denmark, Norway, Germany, Italy and France have also been affected, and trading on some has stopped for a while.
New York bank the statement said: “One of our traders made a mistake when entering the transaction. Within minutes, we discovered the error and corrected it. ”
Sweden’s financial oversight body says it is investigating the collapse and is in contact with the US stock market Nasdaqmanaging the Stockholm Stock Exchange.