BLANTYRE (Reuters) - Malawi's year-on-year headline inflation accelerated to 34.6 percent year-on-year in December from 33.3 percent in November, driven mainly by higher food prices, the National Statistical Office said on thursday"The increase is emanating from the rise in both food costs at 34.5 percent compared to 5.2 percent and core inflation at 34.5 percent compared to 14.4 percent year-on-year," the NSO said.It said the southern African country's inflation averaged 21.3 percent in 2012, 13.7 percentage points higher than 2011.Finance Minister Ken Lipenga set an inflation target of 18.4 percent for 2012 in his 2012/13 budget statement.