The main share index ended down 0.41 percent or 24.99 points at 6048.18, its lowest close since May 5. It has fallen 1.5 percent in the last three sessions.
The rupee has been on a decline since early last month as foreign investors exited from T-bonds as they have done in other emerging markets after the outlook on the U.S. economy improved, making U.S. Treasury yields more attractive.
Brokers said the cut in Sri Lanka's foreign currency sovereign rating outlook by Moody's also weighed on foreign investor sentiment.
Turnover was at 570.2 million rupees ($4.37 million) on Friday, less than this year's daily average turnover of about 1 billion rupees, according to provisional exchange data. John Keells lost 2.24 percent to 248.20 rupees. ($1 = 130.6000 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Sunil Nair)
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