A Bangladeshi national, one of the prime accused in the rape of a septuagenarian nun inside a convent in West Bengal's Nadia district, was arrested here, police said on Thursday.Bangladeshi national Nazrul Islam, 28, was arrested from Sealdah railway station on Wednesday night. He is a prime accused in the Ranaghat rape case, CID Deputy Inspector General (Operations) Dilip Kumar Adak said.Police in May had arrested two accused from Sealdah station as well. So far, six men have been arrested for the March 14 incident in which a gang stormed the Jesus and Mary Convent in Ranaghat in Nadia district and allegedly raped a 71-year-old nun.The incident had created a nationwide outrage with the Prime Minister's Office (PMO) as well as the National Human Rights Commission (NHRC) taking cognisance of the matter.The survivor subsequently left the state for an undisclosed location.