SEOUL (Reuters) - South Korea’s factory output in September declined from August and unexpectedly shrank on a year-on-year basis, ending a 10-month winning streak, as global chip shortages struck car production. Industrial production last month fell by a seasonally adjusted 0.8%, Statistics Korea data showed on Friday, missing a median 0.3% decline forecast in a Reuters survey. It followed a 0.7% drop in August. A breakdown of data showed production of cars shrank 9.8% from a month earlier, while that of semiconductors and electrical equipments also slumped 1.6% and 5.2%, respectively. “September industrial output was weak as global supply chain disruptions were seen weighing on production in the manufacturing industry and on fewer working days (due to the national thanksgiving Chuseok Holiday),” said Oh Chang-sob, an economist at Hyundai Motor Securities. On an annual basis, factory output unexpectedly contracted 1.8%, missing a 1.4% growth forecast in the poll and down from a 9.7% expansion in August. Friday’s data also showed the service sector output expanded 1.3% month-on-month in September, while retail sales jumped 2.5%. Reporting by Joori Roh; Editing by Christian Schmollinger and Stephen Coates