FRANKFURT—The euro-zone economy barely expanded in the third quarter, raising fresh concerns that the region faces a mix of stagnation, weak prices and high unemployment that threatens to hold back activity for the foreseeable future. Gross domestic product in two of the bloc’s three biggest economies—France and Italy—contracted. Growth in Europe’s largest economy, Germany, slowed sharply. Euro-zone GDP expanded 0.1% from the previous quarter, or 0.4% at an annualized rate, the European Union’s statistics agency Eurostat said Thursday. That is down sharply from roughly 1.2% annualized growth in the second quarter. The euro-zone economy contracted for six-straight quarters from late 2011 through the first three months of this year. Germany’s GDP increased 1.3% in the third quarter from the preceding period on an annualized basis, according to calculations by J.P. Morgan matching economists’ forecasts. That marked a significant slowdown from the second quarter, when German GDP swelled 2.9% annualized, […]