ATHEN--Greece's economy expanded at a slightly faster pace in the third quarter than previously expected, the national statistics service said Friday, confirming that Greece has returned to growth after six years of recession.

According to revised data by the Hellenic Statistical Authority, or Elstat, gross domestic product in the July to September quarter rose 1.9% from a year earlier. In its previous third quarter flash estimate from earlier this month, Elstat said the economy grew at a 1.7% rate.

Accounting for seasonal adjustments, Elstat said GDP rose 0.7% from the second quarter, unchanged from its previous estimate.

Until this year, Greece's economy has been wallowing in a deep recession, made worse by waves of austerity measures to fix its public finances in exchange for two successive international bailouts worth 240 billion euros ($300 billion). Six years of recession have shrunk Greece's economy by roughly 30% since its peak in early 2008 and left more than a quarter of the workforce unemployed.

But a record tourist season, that saw the arrival of more than 21 million overseas visitors this year, helped return Greece's economy back to growth. Fresh retail sales data for September, also released Friday, also show a modest improvement in consumer sentiment.

According to the data, retail sales volumes at constant prices rose 2.2% on year in September, as shoppers spent more at supermarkets and at book and stationary stores at the start of the back-to-school season. But on a month-on-month basis, retail sales were down 9% from August as the summer discounting season drew to an end.

Technically, Greece's economy exited recession in the second quarter, growing 0.4%, according to revised year-on-year data that follow Europe-wide updates to national accounting methodologies. On a seasonally adjusted basis, and using the new accounting methodologies, Greece's economy also recorded a 0.8% quarter-on-quarter growth rate in the first quarter of the year.

For the full year, Greece and its international creditors--the European Commission, the European Central Bank and the International Monetary Fund--expect the economy to grow 0.6% before picking up to expand 2.9% in 2015.

Some private sector economists expect Greece's economy to surpass the official forecasts for this year.

Write to Alkman Granitsas at alkman.granitsas@wsj.com

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