Singapore shares closed lower on Monday, tracking mixed fortunes in the regional markets as investors took a step back following mixed regional activity in the previous rally, heightened by the US Federal Reserve's decision to cut interest rates.

The Straits Times Index (STI), a key benchmark for the Singapore Exchange, ranged between 4,291.99 and 4,315.70 throughout the day. It ended the session at 4,297.37, down 5.34 points or 0.12% compared to Monday's close.

In company news, shares of Singapore Telecommunications (SGX:Z74) were down nearly 2% as its unit, Optus, responded to a technical failure that impacted triple zero calls across Australia.

Tan Chong International (SGX:T15, HKG:0693) was up over 3% after its subsidiary, Redcliffe Investments, engaged in a series of transactions involving its investment in Subaru (TYO:7270).

Meanwhile, shares of AJJ Medtech (SGX:584) surged over 33% at the close after the company secured a long-term contract worth over SG$2 million.

STI fell 0.1%; SingPost, Seatrium, and Singtel fell 2%; Yangzijiang Shipbuilding fell 1%; Olam rose 2%.