The CSE All-Share Index closed 0.76% higher at 7,333.42.
Sri Lanka reported 2,584 new cases of COVID-19 on Thursday, with the death toll reaching 1,298 and about 1.58% of the country's population fully vaccinated so far, as per Johns Hopkins data.
The CSE All-Share Index rose 0.10% to 7,215.60. The index has climbed 6.5% this year.
Foreign investors were net sellers in the equity market, offloading shares worth 277.4 million Sri Lankan rupees ($1.4 million), according to exchange data.
The CSE All-Share Index fell about 2.29% to close at 7,066.70 points.
Insurance underwriter Ceylinco Insurance Plc and conglomerate Expolanka Holdings Plc were the top drags to the index, falling about 9% and 3.9%, respectively.