Data from national statistics agency ELSTAT on Thursday showed unemployment rose from 16.5 percent in July as a rise in tourism activity in August failed to stem sharp job losses in the economy. More than four-in-ten young people were out of work.
"The rate of deterioration in the labor market topped even the most pessimistic projections during a month when tourism provides support," said Nikos Magginas, an economist at National Bank of Greece.
"At this pace, it will be hard to see unemployment below 18 percent in the last quarter.
Greece's economy is seen shrinking for a fourth consecutive year in 2011, at an annual pace of 5.5 percent. The European Union and International Monetary Fund do not expect a recovery before 2013.
The August reading was sharply higher compared to the same month last year, when unemployment stood at 12.2 percent.
The number of the unemployed grew by almost 50 percent to 907,953. Greek unemployment figures are not adjusted for seasonal factors.
The young continued to be the hardest hit, with the jobless rate in the 15-24 category soaring to 43.5 percent, twice its level three years ago.
The average jobless rate in the 17 countries sharing the euro held steady at a seasonally adjusted 10.1 percent in August.