WASHINGTON (MarketWatch) - The import price index in May rose by 0.6% for the second straight month, adding to mounting evidence of higher inflation. Rising gas prices in particular are helping to spur on inflation. Excluding fuel, prices of imported goods advanced a smaller 0.2%, the government said Thursday. The increase in import prices over the past 12 months rose to 4.3% from 3.6%. If fuel is omitted, the increase in import prices over the past year was a more modest 1.9%. Earlier this week, a pair of measures for U.S. consumer and wholesale prices both rose again, underscoring an increase in inflationary pressures that caused the Federal Reserve this week to raise U.S. interest rates for the seventh time since the end of 2015. U.S. export prices also rose 0.6% in May.