Singapore shares tumbled further on Thursday as investors reacted to the US Federal Reserve's decision to keep interest rates unchanged amid a raging trade war.

The Straits Times Index (STI), a key benchmark for the Singapore Exchange, ranged between 3,839.14 and 3,875.41 throughout the day. It ended the session at 3,848.22, down 17.15 points or 0.4% compared to Wednesday's close.

In company news, DBS's (SGX:D05) shares were up under 1% after the financial institution's net profit fell 2% year over year to SG$2.9 billion in the first quarter.

Shares of Riverstone (SGX:AP4) slumped nearly 9% at the close after the company's attributable profit to equity holders declined to 56.4 million Malaysian ringgit during the first quarter of the year from 72.2 million ringgit a year earlier.

Meanwhile, Fortress Minerals (SGX:OAJ) was up nearly 5% at the close after the mining company signed a share and purchase agreement with the company's CEO, Sri Ivan Chee Yew Fei, to acquire a 10% stake in Strategic Venture for a cash consideration of $3 million.