A building has collapsed adjacent to a cinema close to the Wellawatte junction.
Police said several persons have been trapped underneath the rubble while rescue efforts are underway.
According to reports there is risk of the building collapsing further.
Four persons who sustained injuries have been admitted to the Colombo General Hospital while eight others have been admitted to the Kalubowila Teaching Hospital for treatment.
A spokesperson of the hospital said the injured are still being brought into the hospital.