The home secretary in the eastern state of Bihar said the incident was potentially the latest in a spate of anti-Christian activity in parts of India over the past year.

Abducted

The young nun, from the southern state of Tamil Nadu, told police she hired a three-wheeler auto rickshaw taxi in the Bihar town of Chapra to travel to the post office.

She said two men who were in the vehicle abducted her, took her to an orchard, tied her hands to a tree and stripped her.

They then allegedly threatened to rape her, urinated in a bottle and forced her to drink it.

The nun said they asked her how many people she had converted to Christianity and why she did not go back home.

Protests

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The incident has angered India's Christian community and the president of the United Christian Forum for Human Rights, Archbishop Alan de Lastic, has written a letter of protest to the prime minister.

"While you are busy during the parliamentary elections, the attacks on the Christian community are still continuing," the letter said.

The Archbishop of Patna, the Bihar state capital, called it an ugly and inhuman act.

The state police chief is heading the investigations into the complaint, lodged by the church.

The nun belonged to the congregation of the Sisters of the Immaculate Heart and had recently travelled to Bihar from Pondicherry, in south India.

Election issue

The police say it is not known yet whether the incident could be linked to the Hindu extremism the church maintains has been the motivation for anti-Christian attacks elsewhere in India during the past year, or whether this was a more local law and order issue.

In the most notorious of the attacks in Orissa, an Australian missionary and his two young sons were burnt to death.

The man accused of being behind the January attack remains at large, an issue which has been taken up in the campaigning for the general election currently taking place in India.

Earlier this month a Catholic priest was killed by unidentified assailants in the same area of Orissa.