A volunteer rescue worker told Asian Mirror from Kotikawatte that some people were still refusing to leave their homes for fear of robbers.
They fear that their houses will be robbed after they are abandoned, he said.
Many parts of the low-lying areas along the Kelani basin were under water and people could be accessed by boats.
Prime Minister Ranil Wickremesinghe urged the people to leave for safety, adding that the tri-forces will guarantee the safety of their homes.