Rustkacheva, a Russian national had been dragged to the beach and raped, media reports said.
Sri Lankan authorities have promised an impartial probe and no meddling in the investigation.
Sri Lanka does not have an independent public service and legal analysts and activists have viewed with concern a steady deterioration of rule of law and justice and growing selective implementation of law over several decades.
Khuram Shaikh, a Briton who is working for the Red Cross in Palestine was killed after being shot and cut with broken bottles by a group led by local politician and his and his friend Victoria Rustkacheva, raped, according to media reports.
A British high commission statement said Nasir Shaikh, the brother of the slain tourist who came to oversee the repatriation of the body met the police.
"From the assurances I have received today I am confident that the Sri Lankan authorities have what they need to bring those responsible for the brutal murder of my brother, and the vicious