Foreign investors bought shares for a 24th straight session, buying a net 318.6 million rupees ($2.10 million) worth of stocks on Wednesday.

They have snapped up a net 12.4 billion rupees worth equities during the period and a net 14.9 billion rupees worth year-to-date.

The Colombo stock index ended 0.36 percent firmer at 6,516.26.

The index has climbed 9.1 percent in the 19 sessions through Wednesday, having risen for 16 sessions in that period.

It added 2.1 percent last week, marking its fourth week of gains.

"Foreigners are very active and buying aggressively, while local investors are cautiously waiting to buy," said Dimantha Mathew, head of research, First Capital Equities (Pvt) Ltd.

Turnover stood at 1.44 billion rupees, higher than this year's daily average of 882 million rupees.

Market heavyweight John Keells Holdings gained 1.1 percent, while Ceylon Tobacco Company rose 0.6 percent.