A 46-year-old man was arrested today on suspicion of torture carried out during the civil war in Nepal, Scotland Yard said.
Counter-terrorism officers held the man this morning in St Leonards, and he is being questioned at a police station in the county.
The unit is responsible for investigating alleged war crimes and human rights abuses, and today's arrest relates to claims that acts of torture were committed in Nepal in 2005.
Officers are searching a residential address in St Leonards the Metropolitan Police said.
At least 13,000 people died during the conflict in Nepal, which lasted for a decade until 2006.
The United Nations said that up to 9,000 serious human rights violations could have been committed during the war, including forced disappearances, torture and executions.
The man is believed to have been a supporter of the Nepalese government during the conflict who has now been living in the UK for some years.
If charged, he could face prosecution under British law because torture is an offence of "universal jurisdiction".