ACCRA (Reuters) - Ghana trimmed its economic growth forecast for this year to 6.9 percent on Wednesday after data showed a marked slowdown in second-quarter growth year-on-year, the country's statistical service said on Wednesday. Ghana's unadjusted gross domestic product (GDP) growth decelerated to 5.3 percent year-on-year in the second quarter, sharply down from a revised 10.8 percent in the same period last year, the service said. Government statistician Philomena Nyarko said the full-year growth forecast was cut from 7.1 percent after first-half growth figures gave a clearer indication of the economy's trajectory than the finance ministry's earlier estimate. Ghana's economy grew by a revised 7.6 percent in 2013, the service said. Excluding oil, last year's growth was 7.3 percent. Ghana's economy has expanded rapidly in recent years because of its exports of gold, cocoa and oil but the country has been hit this year by fiscal problems including escalating inflation and a currency that has fallen sharply. Earlier on Wednesday, the statistics office said Ghana's annual consumer price inflation rose to a fresh four-year high of 16.5 percent in September from 15.9 percent the previous month. The government is in talks with the International Monetary Fund on a possible financial assistance programme that could begin in January.