The Swiss franc rose to its strongest in a week against the euro on Thursday, lifted by a rise in risk aversion after the Federal Reserve's chairman described the outlook for the US economy as "uncertain." The franc was up 0.2 percent against the euro compared to the New York close, trading at 1.3368 per euro at 0637 GMT, its strongest since July 13. The franc also climbed against the dollar to 1.0485 per dollar.