European natural-gas prices trade above 68 euros a megawatt-hour, their highest in more than three years, as supply constraints and low storage levels continue to worry investors. Inventories across the European Union are currently 63% full, well below the five-year average of 80%. “At the current rate, it will be difficult for the EU to hit even the lower storage target of 75% ahead of the heating season,” analysts at ING say. “This raises the prospects of forced buying, increasing upside risk for gas prices.” In early trading, the benchmark Dutch TTF contract slips 0.2% to 68.10 euros a megawatt-hour, but is up 7% on the week.