* Data to be released on Friday by statistics agency
* President reports Jan-May economic activity of 4.1 pct
BUENOS AIRES, July 17 (Reuters) - Argentina's economic activity jumped 7.8 percent in May from a year earlier , President Cristina Fernandez said in a televised speech on Wednesday.
Fernandez announced the data two days earlier than it was to have been released by the national statistics institute. The figure came in well above the 6.1 percent expected by a Reuters poll of economists.
Between January and May, Argentina's economy expanded 4.1 percent versus the same period last year, Fernandez said. In April, economic activity grew a faster-than-expected 7 percent.
The monthly EMAE economic activity index is a close proxy for gross domestic product, which is reported quarterly. The EMAE figures are always revised after the GDP numbers are released to put them in line.
Argentina is widely accused of manipulating inflation data and, to a lesser extent, growth data. It faces potential sanctions by the International Monetary Fund, which has issued a "declaration of censure" against Argentina over the quality of its statistics.
Latin America's No. 3 economy grew just 1.9 percent in 2012 versus 8.9 percent in 2011, according to official data. This reflected weak global demand for its exports, a poor grains harvest, high inflation and the negative impact of currency and trade controls on investment.
More recent data indicates the economy is rebounding thanks to the construction and auto sectors and a better grains harvest.