Singapore shares remained in the red zone on Monday amid stalled U.S.-Iran peace negotiations.

The Straits Times Index (STI), a key benchmark for the Singapore Exchange, ranged between 4,885.96 and 4,925.71 throughout the day. It ended the session at 4,892.73, down 30.13 points or 0.6% compared to Friday's close.

Addvalue up 36%; AEM SGD up 11%; Yanlord Land up 6%; AvePoint up over 3%; ST Engineering down 2%; Seatrium, Keppel down around 3%.

In economic news, Singapore's manufacturing output jumped 10.1% in March, backed by strong growth across almost all clusters, according to the city-state's Department of Statistics.

On the corporate front, shares of Addvalue Technologies (SGX:A31) zoomed over 36% at the close as the company filed an application to the SGX-ST for a proposed spin-off of its Inter-Satellite Data Relay System business on Nasdaq.

Mooreast's (SGX:1V3) shares closed over 6% higher as its subsidiary, Mooreast Asia, granted HLMG-Nuform System an option to purchase its leasehold property in Singapore for SG$29.7 million.

Meanwhile, shares of MoneyMax Financial Services (SGX:5WJ) were up nearly 3% at the close as it raised around SG$43.4 million through the issuance of shares.