Singapore shares closed lower on Thursday, tracking losses across the region as the U.S. issued Iran a 15-point plan to end the war.

The proposal was reportedly delivered to Iranian officials through Pakistan, with Iran "responding negatively" to it.

The Straits Times Index (STI), a key benchmark for the Singapore Exchange, ranged between 4,887.76 and 4,934.54 throughout the day. It ended the session at 4,887.76, down 16.78 points or 0.3% compared with Wednesday's close.

In economic news, Singapore's manufacturing output edged down 0.1% year-on-year in February, due to decreased outputs from several clusters, EDB Singapore reported.

On the corporate front, shares of Micro-Mechanics (SGX:5DD) surged nearly 7% at the close as it bought back 300 shares in the open market on Wednesday for SG$614.

Lendlease Global Commercial REIT (SGX:JYEU) was down nearly 2% as it issued 352.4 million new units on Thursday at SG$0.558 per unit.

Meanwhile, Stoneweg Europe Stapled Trust (SGX:SET) closed over 1% lower as it invested an additional 50 million euros in AiOnX, a private European data center platform, via a mandatory convertible loan.