U.S. import prices rose more than expected in March to post their largest increase in more than 1-1/2 years, driven by a surge in imported petroleum costs and higher food prices, a government report showed on Tuesday.

Overall import prices jumped 2.7 percent, a sixth straight month of gains, the Labor Department said. The increase outstripped economists' forecasts for a 2.2 percent increase and followed a 1.4 percent rise in February.

But excluding volatile petroleum and food prices, import prices were up only a fractional 0.3 percent after rising 0.6 percent the prior month. In the 12 months to March, overall import prices surged 9.7 percent, the largest increase since April.

The monthly rise in import prices reflected a 10.5 percent surge in petroleum, the biggest increase since June 2009, which followed a rise of 4.0 percent in February. Imported food prices increased 4.2 percent, the largest advance since July 1994, after rising 0.7 percent in February.

(Reporting by Lucia Mutikani, Editing by Chizu Nomiyama)