SINGAPORE, May 25 (Reuters) - Singapore’s economy expanded more than initially estimated in the first quarter, helped by stronger-than-expected manufacturing, official data showed on Tuesday. Gross domestic product (GDP) grew 1.3% year-on-year in the first quarter, the Ministry of Trade and Industry (MTI) said, higher than the 0.2% growth seen in the government’s advance estimate. Analysts had expected a 0.9% increase, according to a Reuters poll. On a quarter-on-quarter seasonally-adjusted basis, the economy expanded by 3.1% in the first quarter. The MTI said it would maintain 2021 GDP growth forecast at 4% to 6% amid significant uncertainties arising from the COVID-19 pandemic. (Reporting by Chen Lin and Aradhana Aravindan in Singapore; Editing by Sam Holmes) Our Standards: The Thomson Reuters Trust Principles.