No reason was given for the change and immigration department officials were not immediately available for comment.
Tourists from all countries except Singapore and Maldives will be required to obtain prior entry visa before their arrival in Sri Lanka either from the Department of Immigration & Emigration in Colombo or from the Sri Lanka missions abroad.
Tourism industry officials said the move could hit tourist arrivals which have been increasing rapidly since the island's 30-year ethnic war ended in May 2009.
Among the highest number of visitors to the island in recent months have been tourists from India who get visa on arrival.