Officials said deaths were reported from the western coastal district of Kalutara, the central southern district of Ratnapura and the southern district of Matara.
"Aid is now getting into the remotest areas which remained inaccessible in the past two days," Health Minister Rajitha Senaratne said.
Despite floodwater clearing in Ratnapura and Matara districts, many villages in Kalutara are still underwater and more rains are expected in the coming days.
Almost half a million people across the nation have been forced from their homes due to the early rainy season downpours.
After a river filled with dangerous wildlife burst its banks in the monsoon, residents to the south of the island were warned of possible crocodile attacks.
The charity Save the Children said about a tenth of those displaced were children below the age of five years.
It raised fears of stagnant flood waters becoming breeding grounds for dengue spreading mosquitos and noted that young children were more vulnerable.
Medical teams were dispatched to the worst-affected areas to help prevent an outbreak of waterborne diseases.
"We have the expertise to deal with this situation," Senaratne said, adding cholera and diarrhoea had been successfully prevented in past floods.
Police spokesman Priyantha Jayakody said multiple landslides were reported in Kalutara, Ratnapura and Matara.
Military spokesman Roshan Senevirathne said more than 2000 military personnel had been deployed to help the police and civilian agencies.
Although 111 people are still missing, the head of the search and rescue mission, Major General Sudantha Ranasinghe, said that he didn't expect to find any more survivors.
The wettest time of the year in Sri Lanka's south is usually from May to September and the island nation also gets heavy rains in the North West monsoonal season from November to February.
