According the Colombo National Hospital, the one death was due to cardiac arrest, Xinhua news agency reported.
While eight were hospitalised from food poisoning, eight others had sustained minor injuries and over 70 were hospitalised due to excessive alcohol consumption.
Sri Lanka's Joint Opposition held the rally on Wednesday to protest against the rising cost of living, the government's economic policies and call for a snap parliamentary poll.
The protest was organised by former President Mahinda Rajapaksa's eldest son and parliamentarian, Namal Rajapaksa. The former president and his brother Gotabhaya Rajapaksa also participated in the rally.
Joint Opposition legislators said thousands had attended the rally but an exact figure could not be confirmed.
The protest which started on Wednesday afternoon, ended early on Thursday.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
