Philippines president Rodrigo Duterte has revealed he ordered an investigation into an Australian nun for 'disorderly conduct', in a move against what he called 'undesirable' foreigners. The country's bishops have in turn hit out at Duterte's 'despotic government' and condemned 'unspeakable violence' being committed against religious institutions.

Sister Patricia Fox, 71, was taken from her house and detained this week at Manila's immigration bureau for nearly 24 hours before being released on Tuesday. The nun, who coordinates the Catholic community Notre Dame de Sion, has been part of rallies urging the release of political prisoners and advocating for human rights and protection for the poor, but has denied active politicking.

Duterte said on Wednesday: 'I ordered her to be investigated, not deported at once, not arrested, but to invite her to an investigation for a disorderly conduct.'

He accused Fox of 'a violation of sovereignty' and said: 'You insult me under the cloak of being a Catholic priest, and you are a foreigner. Who are you?'

He added: 'You do not have that right to criticise us. Do not insult my country. We never did that to Australia. We never did that to [a] European country. Why don't you criticise your own government, the way you handle the refugees, hungry and dying and you turn them back to the open sea?' Australia has been criticised for its treatment of refugees, with hundreds of asylum seekers stranded at the country's controversial off-shore detention centre on Papua New Guinea. 

Duterte said he had the right to deport or refuse entry to an 'undesirable alien'. 

On Thursday the Ecumenical Bishops' Forum, the largest cross-denominational coalition in the Philippines, said the detention of Fox was 'the most recent blow against church workers and religious institutions', according to UCA News.

The joint statement expressed 'outrage at this evil-doing' by the Philippines government, describing 'perilous times' for the church in the country and condemning 'unspeakable violence' committed against Christians.

The statement added: 'The persecution of church people does not only reveal the sword of a despotic government that seeks to suppress the church's role as a moral compass of society. It is a demonstration of [the Duterte] administration's noxious attempts to criminalise legitimate dissent.'

Clerics in the country have long spoken out against Duterte's hard-line 'war on drugs' that has caused a 'reign of terror' amongst the nation's poor, according to Catholic bishops. Thousands of suspected drug dealers and users have been killed since Duterte launched what critics have called an illegal crusade against narcotics in 2016.

The bishops' statement implored Christians 'to boldly resist state violence and political oppression, and continue to stand up for and work in solidarity with the poor, deprived and oppressed'.

Additional reporting by Reuters