The main share index fell 0.33 percent, or 19.78 points, to 5,928.97, from its one-week closing high on Friday.
Shares in John Keells Holdings fell 1.89 percent to 218.10 rupees while Carson Cumberbatch Plc ended 5.04 percent weaker at 375.00 rupees.
John Keells, which has been raising $299 million by selling rights and warrants to fund a $850 million resort project, on Friday said its rights issue was substantially oversubscribed.
Foreign investors were net sellers of 91.7 million rupees worth of shares on Monday, snapping five straight sessions of foreign inflows. However, they have been net buyers worth 22.73 billion rupees so far this year.
The day's turnover was 372.5 million rupees ($2.85 million), well below this year's daily average of 875.8 million rupees.
($1 = 130.6500 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Anupama Dwivedi)
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