* Import prices increase 0.7 percent in September
* Import prices excluding petroleum rise 0.3 percent
* Export prices advance 0.8 percent
WASHINGTON, Oct 17 (Reuters) - U.S. import prices for September recorded their biggest increase in more than a year amid rising petroleum and food costs, but underlying imported inflation remained modest.
The Labor Department said on Tuesday that import prices jumped 0.7 percent last month, the biggest gain since June 2016, after an unrevised 0.6 percent rise in August.
Economists polled by Reuters had forecast import prices increasing 0.5 percent in September.
In the 12 months through September, import prices climbed 2.7 percent after advancing 2.1 percent in August. The year-on-year rise in import prices peaked at 4.7 percent in February, which was the biggest advance in five years.
U.S. financial markets were little moved by the data.
Last month, prices for imported petroleum increased 4.5 percent after rising 5.0 percent in August. Food prices surged 1.8 percent, the largest gain since July 2016, after edging up 0.2 percent in August.
Import prices excluding petroleum rose 0.3 percent after a similar gain in August. They increased 1.2 percent in the 12 months through September. The increase in import prices excluding petroleum has remained moderate despite the dollar weakening more than 6 percent against the currencies of the United States' main trading partners this year.
The cost of imported goods from China was unchanged in September after slipping 0.1 percent in August. Prices for imports from China fell 0.7 percent on a year-on-year basis.
The report also showed export prices rose 0.8 percent in September, the largest increase since June 2016, after gaining 0.7 percent in August. Export prices were boosted by an increase in prices for nonagricultural commodities, which offset a decline in the cost of agricultural exports. Export prices increased 2.9 percent year-on-year in September after rising 2.4 percent in August.
(Reporting By Lucia Mutikani; Editing by Chizu Nomiyama and Andrea Ricci)