SINGAPORE, Oct 14 (Reuters) - Singapore's economy contracted slightly more than expected in the third quarter from a year earlier, preliminary data showed on Wednesday.

Gross domestic product (GDP) shrank 7% in July-September on a year-on-year basis, the Ministry of Trade and Industry said in a statement. Economists polled by Reuters had expected a decline of 6.8%.

GDP grew 7.9% on a quarter-on-quarter seasonally adjusted basis in July-September. The trade ministry said it would only be reporting non-annualised quarter-on-quarter data from the third quarter, and not previously reported annualised data. (Reporting by Chen Lin; Editing by Sam Holmes)