Rape is rape and should not be politicised, Indian Prime Minister Narendra Modi said on Wednesday, adding that recent sexual assaults were a matter of shame for the nation.

Modi was greeted on a visit to London by hundreds of noisy protesters, demonstrating against a rising tide of sexual violence at home including two particularly brutal rapes.

"Rape is rape ... How can we accept this?" Modi said through a translator at a diaspora event, adding that people needed to ask more questions of the perpetrators.

"This is a matter of great concern for the country and these sinners are somebody's sons... The rape of a (daughter) is a matter of worry, a shame for the country."

In Kathua district of Jammu and Kashmir, an eight-year-old child from a minority nomadic community was allegedly held in captivity in a small village temple for a week in January this year during which she was kept sedated and sexually assaulted before being bludgeoned to death.

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Eight persons, including a juvenile, were arrested in the case. The trial in the case began on Monday.

In Uttar Pradesh's Unnao, a teenage girl alleged that she was raped by a ruling BJP MLA who has been arrested by the CBI, which is probing the case.

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In Surat, the body of a girl, who could be between nine and 11 years of age, was found recently with doctors believing that she was possibly held captive, tortured and raped over a period of time.