The 19-year old was found dead on Thursday in the stairwell of an apartment building in Colombo, where her parents have a flat.
According to Sri Lankan newspapers, the 21-year old suspect is a former classmate of the murdered girl. Other papers say he is her former boyfriend.
Swedish news agency TT quoted a police official in Colombo, who said that the man had admitted murdering the 19-year old. He added that the killing was preceded by an argument between a man and a woman.
The man will appear in court on Monday, reports Dagens Nyheter.