Ucanews.com reported immigration officers arrested Sister Patricia Fox, Philippine superior of the Sisters of Our Lady of Sion, at her convent in Quezon City April 16.

Although the prosecutor in charge "found no probable cause" for her arrest and ordered the nun's "release for further investigation," immigration officials insisted on the nun's detention.

They said Sister Fox failed to surrender her passport to the bureau. The nun said her documents were with a travel agency.

Sister Fox was detained at the bureau's intelligence division but was released April 17.

Immigration officials have accused the nun, who has worked in rural communities for 27 years, of being an "undesirable alien" for joining protest rallies and visiting political prisoners.

Among the evidence presented by authorities are pictures of the nun taken during a jail visit in the southern Philippines with a banner that reads "Stop Killing Farmers."

The nun also joined a recent fact-finding and solidarity mission that investigated alleged human rights abuses committed against farmers and tribal people in the southern Philippines.

She told ucanews.com that part of her missionary work is "to immerse with the poorest of the poor in any event."

"Our mission includes listening to the narratives of people, especially poor farmers and indigenous people," she said. "We go to places where we find them."

The nun said her presence at demonstrations "was not a form of protest against anyone in the government but merely accompanying the poor in their struggle."

Sister Fox, who holds a Philippine missionary visa, is former national coordinator of the Rural Missionaries of the Philippines and volunteer staff of the farm workers union.

Human rights and church groups expressed alarm over her arrest.

Manila Auxiliary Bishop Broderick Pabillo said Sister Fox "is too old to run from the government or from whatever allegations they are accusing her of" and called her arrest a "form of persecution and harassment."

"This is political," said Bishop Pabillo. "The government is trying to intimidate individuals and groups who are in pursuit of social justice for the oppressed and the poor."

Father Benjamin Alforque of the Promotion of Church People's Response said the arrest is a violation of the nun's fundamental rights.

"When has it become a crime for church people to exercise their right to preach the Gospel and accompany the poor?" asked the priest.

The Rural Missionaries of the Philippines said Sister Fox's arrest was part of the Philippine government's crackdown on human rights defenders.

"It is disheartening that (Sister Fox) is being attacked by our government when all she does is serve and support the Filipino rural poor," said Sister Elen Belardo, national coordinator of the group.

Other foreigners have been arrested for solidarity activities in the Philippines.

Cristina Palabay, secretary-general of the human rights group Karapatan, said the arrest of Sister Fox and threats against international human rights advocates "are clear and blatant forms of violation on the exercise of people's right to extend international solidarity to victims of rights violations."