U.K. stocks closed slightly lower Wednesday as a brief surge in the pound yanked the benchmark FTSE 100 to session lows, but retail shares added to gains after monthly British retail sales leapt past expectations. All the moves were made before Wednesday's marquee event for global markets took place: the U.S. Federal Reserve's September policy decision.

U.S. stock benchmarks ended a volatile session mostly in the green, with the Dow industrials and the S&P 500 carving out fresh all-time highs, as the Federal Reserve announced that, for the first time in nine years, it would start reducing the size of its $4.5 trillion asset portfolio commencing in October.

Asian stocks were split early on whether to rise or fall in the wake of the Federal Reserve's overnight statements on policy and economic projections. Japan was again a standout, with equities building on this week's two-year highs as the yen continued to retreat. Meanwhile, Australia underperformed as metal prices fell and utilities stocks slid.