Singapore shares climbed on Monday, bucking the trend in regional markets as investors grew anxious over US President Donald Trump's impending tariff deadline.

The Straits Times Index, a key benchmark for the Singapore Exchange, ranged between 4,011.88 and 4,031.86 throughout the day. It ended the session at 4,031.86, up 18.24 points or 0.5% compared to Friday's close.

In economic news, Singapore's official foreign exchange reserves declined to SG$515.8 billion in June, from SG$518.1 billion in the preceding month, according to preliminary data from the Monetary Authority of Singapore.

In company news, shares of Addvalue Technologies (SGX:A31) were up nearly 7% at the close after the company said it secured new orders worth about $2.1 million for its InterSatellite Data Relay System (IDRS) terminals.

Nanofilm Technologies (SGX:MZH) was down over 2% as the company entered into a sale and purchase agreement with Venzio Investments to acquire a 35% stake in Sydrogen Energy.

Meanwhile, shares of United Overseas Bank (SGX:U11) closed nearly 1% higher, despite the bank being fined SG$5.6 million by the Monetary Authority of Singapore for anti-money laundering-related breaches.