Pope Francis has denounced the 'thick darkness' of violence and murder in Colombia.

The Pope was preaching to more than 1 million people at Mass in Bogotá on his visit to the conflict-ridden country. Those who showed up to take in his message included victims of the conflict in Colombia, as well as many refugees from violence in neighbouring Venezuela.

The Pope, who said Mass in Simon Bolivar Park, spoke of a 'darkness' that he described as a 'thirst for vengeance and the hatred which stains the hands of those who would right wrongs on their own authority, the darkness of those who become numb to the pain of so many victims'.

A peace agreement between the government and Revolutionary Armed Forces of Colombia (FARC) rebels after a five-year conflict, along with a bilateral ceasefire with the National Liberation Army (ELN) left-wing rebel group, have led to a fragile three-month peace in Colombia.

Pope Francis hopes to bolster this during his visit, even as paramilitary and drug-related violence continues to disrupt neighourhoods.

Pope Francis urged the faithful to trust God 'whose word is fruitful even where the hostility of human darkness' threatenes to destroy, Vatican Radip reported. 'We need to call out to one another, to signal each other, to see each other again as brothers and sisters, companions on the way, partners in this common cause which is the homeland'.

He called on them to leave selfishness, fears and paralysis behind and become 'artisans of peace, promoters of life'. 

Pope Francis arrived in Colombia on Wednesday, his 20th foreign trip since becmoing Pope in 2013 and the fifth he has made to his native Latin America.

He will visit Villavicencio, Medellin and Cartagena.

Speaking to reporters on the plane to Colombia on Wednesday, Francis said the trip was 'a bit special because it is being made to help Colombia go forward on its path to peace.'

On arrival he told the crowd, who endured torrential rain to see him, 'Don't let anyone steal your hope.'

A statement from the ELN said the Pope's presence would contribute to finding a lasting peace agreement.

He also encountered opposition from critics such as former president Alvaro Uribe who wrote an open letter denouncing the FARC peace deal and saying the rebels had been given 'total impunity' in spite of terrible crimes.

Christian Aid however was among those who welcomed the peace message. At the same time, it said that with 7 million internally displaced people, Colombia has the largest internally displaced population in the world and those responsible must be prosecuted.

Thomas Mortensen, Christian Aid's country manager for Colombia, said: 'It is fantastic to welcome Pope Francis to Colombia, for him to show solidarity and hope to the millions of people forced far from their homes and loved ones in Colombia. We hope that his visit can make society more sensitive to the immense suffering of the millions of people who have fled their homes.

'Very few people know that Colombia has the world's highest number of internally displaced people (IDPs) and that these 7 million people are suffering tremendously, because being displaced affects all aspects of life, including communities, rights and education. We need to make the humanitarian crisis known to the outside world and act collectively, so that these people can return to their land, and be properly compensated, and gain access to their rights.

'To stop displacements, we also need to ensure that those responsible for the displacements are prosecuted, including the less visible criminals like politicians, businesspeople and public servants who have collaborated with paramilitaries.'

 Pope Francis is also attracting criticism from ultra-conservative Catholics who say the visit is 'non grata' and that Francis is a 'false pope, a false prophet'.

 Last night, Pope Francis met bishops from Venezuela who told him of the 'truly desperate' humanitarian crisis their country is enduring.