One of Sri Lanka's highest-ranking Buddhist monks has been arrested and sent to remand prison over the alleged rape and sexual assault of a 15-year-old girl. 

The Venerable Pallegama Hemarathana Thero holds one of the most revered positions in the Buddhist world - the chief prelate or custodian of eight sacred sites in Sri Lanka. 

He was arrested following a submission from the country's child protection authority, which had previously criticised police for not arresting him despite being named as a suspect in the case. 

Pallegama Hemarathana has not publicly commented on the charges. He will appear in court on 12 May.

The alleged victim's mother was also arrested and remanded to custody after being charged with aiding and abetting the abuse. 

Pallegama Hemarathana was receiving treatment at a private hospital in Colombo when he was arrested on Saturday. The magistrate determined that he should be transferred to the Colombo prison hospital. 

He also issued an order to immigration authorities to ensure that Pallegama Hemarathana did not try to flee the country. 

It is unusual to see Buddhist monks - much less such a high-ranking figure - arrested in Sri Lanka, where they are both politically powerful and venerated by society.