Sept 28 (Reuters) - Slovak producer prices rose 0.6 percent month-on-month in August, above market expectations, putting the annual inflation rate for factory-gate costs (PPI) at 8.8 percent, data showed on Thursday. PRODUCER PRICES Aug 06 July 06 Aug 05 pct change month/month +0.6 +0.6 +0.8 pct change year/year +8.8 +9.0 +5.6 NOTE. Analysts polled by Reuters had forecast a producer price rise of 0.3 percent on a monthly basis in August, and 8.5 percent on an annual basis <SK/ECON04>. All data are subject to revision. (Reporting by Martin Santa, in Bratislava) ((For past economic data and analysts' forecasts, double click on <SK/ECON01>)) ((Editing by Alan Crosby; editorial@reuters.sk; Reuters Messaging: martin.santa.reuters.com@reuters.net; +421 2 5341 8402)) Keywords: ECONOMY SLOVAKIA PPI