However, foreign investors bought into risky assets, limiting the downside.

The Colombo stock index ended 0.16 percent lower at 6,684.47, its lowest close since June 19, and its fourth straight session of falls.

"Turnover was healthy and we still see foreign interest in equities. We see the support level at 6,650," said Hussain Gani, deputy CEO at Softlogic Stockbrokers.

Foreign investors bought shares worth net 346.3 million rupees ($2.25 million) on Wednesday, extending the year-to-date net foreign inflow to 24.8 billion rupees worth of equities.

Turnover was 1 billion rupees, higher than this year's daily average of 914.1 million rupees.

Shares of Ceylon Tobacco Company fell 1.6 percent, while market heavyweight John Keells Holdings closed 0.6 percent weaker.