Pope Francis called for unity in the Catholic Church and blamed its divisions on the devil.

It was the second time in as many days that Francis warned about the destructive work of the devil after making headlines recently by seeming to deny the existence of hell.

Francis made the comments during a Mass he celebrated along with 550 'missionaries of mercy,' the army of priests he formed during his 2015-2016 Jubilee of Mercy to highlight the sacrament of reconciliation around the globe.

The Pope said Catholics should treat compassion for migrants and the poor as equal to opposing abortion.

The Argentine pontiff warned followers to not 'relativise' their faith and giving some rules 'excessive importance' and treating others as 'secondary'.

The 61-year-old issued a strong rebuke to critics of his emphasis on helping others who complained he was not strong enough on moral teachings.

Pope Francis said Catholics should treat compassion for migrants and the poor as equal to opposing abortion

'Not infrequently, contrary to the promptings of the (Holy) Spirit, the life of the Church can become a museum piece or the possession of a select few,' he said.

'This can occur when some groups of Christians give excessive importance to certain rules, customs or ways of acting.'

Pope Francis was writing in his third apostolic exhortation - a 100-page guideline on how Catholics could strive for 'holiness' in the modern world.

He encouraged believers to be 'the saint next door' focusing on mercy and charity as Jesus did, rather than upholding strict rules.

The exhortation was widely seen as a dig at conservative Catholics in the U.S. and elsewhere who staunchly upheld tradition on abortion, homosexuality, and divorce while pushing anti-migrant laws.

The pope accused them of being caught in 'the thicket of precepts and prescriptions' and disregarding those less fortunate.

Pope Francis' key points Pope Francis on the Devil: 'We should not think of the devil as a myth, a representation, a symbol, a figure of speech or an idea. This mistake would lead us to let down our guard, to grow careless and end up more vulnerable' Pope Francis on migrants: 'For a Christian the only proper attitude is to stand in the shoes of those brothers and sisters of ours who risk their lives to offer a future to their children. Can we not realize that this is exactly what Jesus demands of us, when he tells us that in welcoming the stranger we welcome him?' Pope Francis on social media: 'The saints do not waste energy complaining about the failings of others; they can hold their tongue before the faults of their brothers and sisters, and avoid the verbal violence that demeans and mistreats others' Pope Francis on being a 'saint next door': 'I like to contemplate the holiness present in the patience of God's people: in those parents who raise their children with immense love, in those men and women who work hard to support their families, in the sick, in elderly religious who never lose their smile' Pope Francis on compassion: 'Equally sacred, however, are the lives of the poor, those already born, the destitute, the abandoned and the underprivileged' Pope Francis on extremists: 'If I speak about Islamic violence. I need to speak about Catholic violence. One thing is true. I believe that in almost all religions, there is always a small fundamentalist group. We have them, too' Pope Francis on consumerism: 'We will find it hard to feel and show any real concern for those in need, unless we are able to cultivate a certain simplicity of life, resisting the feverish demands of a consumer society, which leave us impoverished and unsatisfied, anxious to have it all now.... we can waste precious time and become indifferent to the suffering flesh of our brothers and sisters' Pope Francis on prayer: 'I do not believe in holiness without prayer, even though that prayer need not be lengthy or involve intense emotions' Pope Francis on inequality: 'We cannot uphold an ideal of holiness that would ignore injustice in a world where some revel, spend with abandon and live only for the latest consumer goods, even as others look on from afar, living their entire lives in abject poverty' Pope Francis on slandering each other: 'It is striking that at times, in claiming to uphold the other commandments, they completely ignore the eighth, which forbids bearing false witness or lying, and ruthlessly vilify others' Advertisement

The 61-year-old issued a strong rebuke to critics of his emphasis on helping others who complained he was not strong enough on moral teachings

'Our defence of the innocent unborn, for example, needs to be clear, firm and passionate, for at stake is the dignity of a human life, which is always sacred and demands love for each person, regardless of his or her stage of development,' he wrote.

'Equally sacred, however, are the lives of the poor, those already born, the destitute, the abandoned and the underprivileged.

'The vulnerable infirm and the elderly exposed to covert euthanasia, the victims of human trafficking, new forms of slavery, and every form of rejection.'

'We cannot uphold an ideal of holiness that would ignore injustice in a world where some revel, spend with abandon and live only for the latest consumer goods, even as others look on from afar, living their entire lives in abject poverty.'

Pope Francis stressed this included the plight of people fleeing war, persecution and poverty, putting him at odds with a wave of anti-immigrant sentiment in many parts of the world.

'Some Catholics consider the situation of migrants to be a secondary issue,' he wrote.

'Can we not realize that this is exactly what Jesus demands of us, when he tells us that in welcoming the stranger we welcome him?' he said

Citing a passage from the Old Testament urging the welcoming of foreigners, Francis remarked sharply that the issue was not 'a notion invented by some pope, or a momentary fad'

'That a politician looking for votes might say such a thing is understandable, but not a Christian for whom the only proper attitude is to stand in the shoes of those brothers and sisters of ours who risk their lives to offer a future to their children.

'Can we not realize that this is exactly what Jesus demands of us, when he tells us that in welcoming the stranger we welcome him?'

Citing a passage from the Old Testament urging the welcoming of foreigners, Francis remarked sharply that the issue was not 'a notion invented by some pope, or a momentary fad'.

'In today's world too, we are called to follow the path of spiritual wisdom proposed by the prophet Isaiah to show what is pleasing to God,' he said.

Pope Francis then quoted another verse: 'Is it not to share your bread with the hungry and bring the homeless poor into your house; when you see the naked, to cover him...?'

In April 2016, he flew to the Greek island of Lesbos on the frontline of the migrant crisis and returned to Rome with three families of Syrian Muslims.

The first years of Francis' papacy were peppered with strong words against governments, which he has accused of not doing enough to welcome the millions of refugees

In April 2016, he flew to the Greek island of Lesbos on the frontline of the migrant crisis and returned to Rome with three families of Syrian Muslims

The first years of Francis' papacy were peppered with strong words against governments, which he has accused of not doing enough to welcome the millions of refugees and migrants fleeing their home countries.

But over the years, he has moderated his discourse, suggesting that host countries had the right to regulate the number of arrivals according to their capacity to accommodate and integrate foreigners.

'There are those who feel encouraged by the pope's stance on migrants and it is still a majority,' Christophe Dufour, archbishop of the French city of Aix-en-Provence, told AFP.

'And there is a small number who say: 'he is naive, let him come and live among migrants, it is not so simple'.'