The unemployment rate fell to 4.2 percent last month from 4.3 percent in July, the government said Friday, cautioning that the data don't warrant automatic optimism over the economy.

The seasonally adjusted data were virtually in line with market forecasts, which ranged from around 4.2 percent to 4.4 percent. Analysts doubt the momentum will be sustained because there are signs that the economy is being dragged down by weaker exports.

The drop in the jobless rate was mainly caused by unemployed people who stopped looking for work, the Internal Affairs and Communications Ministry said.