Singapore shares closed marginally lower on Wednesday, despite regional indices responding positively to a slight decline in oil prices and in anticipation of the US Federal Reserve's interest rate decision.

The Straits Times Index (STI), a key benchmark for the Singapore Exchange, ranged between 5,627.19 and 5,687.63 throughout the day. It ended the session at 5,635.41, down 3.23 points or 0.1% compared to Tuesday's close.

On the corporate front, shares of Hiap Seng Industries (SGX:1L2) unit secured an extension of its leases for four lots in Tuas Crescent, Singapore, from the Singaporean government agency JTC.

Singapore Airlines (SGX:C6L) was down nearly 2% at the close despite its group passenger traffic rising by 1.5% year on year in August.

Meanwhile, shares of Raffles Education's (SGX:NR7) wholly owned Malaysian subsidiary Raffles K12 was served with two summons seeking enforcement of the arbitration awards by Pembinaan Mitrajaya.