The Colombo Stock Exchange's main index ended 0.25 percent or 13.54 points, weaker at 5,337.71, its lowest close since Sept. 4.
"These is negative sentiment among local investors," said one broker, who declined to be identified, adding that high interest rates had led to a lack of liquidity.
The yield for 364-day T-bills gained for a seventh consecutive week at an auction on Wednesday. Analysts say investors have been shifting to fixed deposits from equities since the central bank kept key policy rates at three-year highs on Nov. 9.,
The day's turnover was 173.3 million rupees ($1.33 million), well below this year's daily average of 900 million rupees. Foreign investors bought a net 7.96 million rupees worth of shares, extending the net foreign inflow this year to 35.5 billion rupees.
The rupee closed firmer at 129.30/35 to the dollar compared with Friday's close of 130.24/28 on foreign inflow into a foreign bank, dealers said. ($1 = 130.1500 Sri Lanka rupees) (Reporting by Shihar Aneez and Ranga Sirilal; Editing by Robert Birsel)