Singapore fell as much as 0.6 percent on Friday, extending losses for a fourth day, as financials and industrials lost ground.
Most of the Asian markets fell, tracking losses in Wall Street overnight as worries grew over U.S. President Donald Trump's ability to push through his economic agenda.
Meanwhile, heightened terror fears after at least 13 people died when a van plowed into pedestrians in Barcelona further tempered risk appetite.
MSCI's broadest index of Asia-Pacific shares outside Japan dropped 0.5 percent.
The Straits Times Index lost 0.52 percent or 17 points to 3,251. It ended 0.31 percent lower on Thursday, taking the year-to-date gains to about 13 percent.
Financials pulled the index lower, with DBS Group Holdings shedding as much as 0.6 percent and Oversea-Chinese Banking Corp declining 0.5 percent.
Among the gainers, Singapore based conglomerate Sembcorp Industries rose 0.6 percent after it increased its stake in India-focused renewable energy business to 72 percent for S$21.4 million.
Shares in cruise ships operator Genting Hong Kong gained about 2 percent despite reporting a higher loss in the first-half, due to increased operating expenses and fuel costs.
About 1.8 billion shares worth S$1.2 billion changed hands, with losers outnumbering gainers 238 to 178.