Foreign investors bought shares worth 810 million rupees on a net basis in the session, bringing the year-to-date net equity inflows to 14.7 billion rupees.

The Colombo stock index gained 0.85 percent at 6,571.65, its highest close since Oct.7.

The index has climbed 10 percent in the 20 sessions through Thursday, having risen for 17 sessions in that period.

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

"Foreign buying is now spreading to some other counters from John Keells. Foreigners see value in these stocks and local investors have been waiting for investor confidence," said Hussain Gani, deputy CEO at Softlogic Stockbrokers.

Turnover stood at 1.84 billion rupees, more than double of this year's daily average of 894.2 million rupees.

Market heavyweight John Keells Holdings gained 1.8 percent, while top lender Commercial Bank of Ceylon rose 1.9 percent.