KOCHI: An Indian Catholic bishop accused of raping a nun has written to the Vatican asking to step down as protests grow in India's Kerala state for him to be arrested.

"Bishop Franco Mulakkal wrote a letter to Holy Father Pope Francis expressing his desire to step aside temporarily and requested to be relieved from the administration of the Diocese," the Diocese of Jalandhar, which he heads, said in a release issued over the weekend.

Kerala police have called Mulakkal for a new round of questioning on Wednesday in the southern Indian state. The bishop has denied wrongdoing.

The nun had accused the bishop of raping her repeatedly over two years from May 2014. She had sent a detailed letter to Pope Francis last week demanding action against the bishop.

The Vatican had no comment on the situation in India.

The case comes at a time when the Christian community, which accounts for 19 percent of the state's population, is reeling under an erosion of trust as sexual abuse cases involving the clergy pile up.

A group of Catholic nuns launched a rare street protest more than a week ago in Kochi, the state's financial hub, demanding justice for the nun. The protest has gathered momentum with Christian bodies, activists, writers and locals joining in.

The group spearheading the protest in Kochi will stage more such protests in various other districts on Tuesday, said Father Augustine Vattoli, coordinator of the Save Our Sisters Action Council.

"We have started the protests demanding the arrest of the bishop. We will not end it without him submitting himself to the law," Vattoli told Reuters, expressing doubts over whether the bishop's offer to step aside was voluntary or at the direction of the Vatican.

The Vatican does not disclose when bishops offer their resignation but only when resignations are accepted by the pope and become official.