Singapore shares sank on Monday, tracking broader regional losses after the US-Iran peace talks in Islamabad ended without a resolution.

The Straits Times Index (STI), a key benchmark for the Singapore Exchange, ranged between 4,965.48 and 4,984.17 throughout the day. It ended the session at 4,984.17, down 5.24 points or 0.1% compared to Friday's close.

Nio up over 7%; PropNex up over 4%; First Resources up 2%; Hong Leong Asia, Bumitama Agri, Sembcorp Ind, iFast up around 1%; SIA, Kep Infra Tr down nearly 1%.

Following the breakdown in discussions, the US military said that it will block all maritime traffic entering and exiting Iranian ports, with Tehran terming the US blockade as "illegal".

On the corporate fund, shares of Mary Chia (SGX:5OX) slumped over 9% at the close as it received a statutory demand from Fullink Capital in respect of an alleged sum of around SG$902,640.

Medtecs International (SGX:546) was down over 2% as the company pulled the plug on its joint venture with Shijiazhuang Hongray, following a strategic review of plans and prevailing market conditions.

Meanwhile, CapitaLand Investment (SGX:9CI) closed its CapitaLand Asia Pacific Credit Program II (ACP II), securing $320 million in total equity commitments.