The consumer price index rose 3.4% in August from a year ago, increasing the chances of a Federal Reserve rate increase next week to more than 80% in traders' eyes.

The inflation figure came in the same as the prior month and as economists surveyed by the Wall Street Journal expected. The core CPI, an inflation figure that excludes volatile food and energy, rose 2.4%.

Both figures confirmed a narrative among investors that inflation has remained too high for the Fed to keep rates at their current level.

Bond yields ticked lower and stocks opened higher, a signal that investors like the idea of a Fed rate increase tamping down inflation. The benchmark 10-year Treasury yield slipped to 4.92% from about 4.94% before the report. Stock indexes are up about 1%, with the Dow industrials up nearly 600 points.

The European Central Bank set the tone Thursday by lifting interest rates, saying it expected inflation to remain above target for an extended period.

The cost of diesel Friday hit $6 a gallon, AAA said, the latest reminder of how rising energy prices are driving inflation. Brent crude futures were volatile, surging overnight to nearly $110 a barrel before falling back to about $104.