The main share index rose 0.6 percent, or 35.50 points, to 5,936.40, from its lowest since Oct. 8 hit in the previous session.
Keells' ordinary shares jumped 3.29 percent to 220.00 rupees, while the conglomerate's rights rose 31.31 percent to 67.10 rupees.
Shares in leading fixed line telephone operator Sri Lanka Telecom Plc rose 2.06 percent to 39.70 rupees.
The day's turnover was 516.8 million rupees ($3.95 million), well below this year's daily average of 872.7 million rupees.
Foreign investors were net buyers of 21.9 million rupees worth of shares on Thursday, extending the year-to-date foreign inflows to 22.81 billion rupees.
($1 = 130.7500 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Anand Basu)
Keywords: MARKETS SRILANKA/INDEX
(Reuters Messaging: email@example.com)(twitter.com/rangab a)