BOGOTA (Reuters) - Pope Francis on Thursday urged Colombians to shun vengeance after a bloody 50-year civil war but said leaders had to enact laws to end the “darkness” of injustice and social inequality that breeds violence.

At the last event of a packed day, the Argentine pontiff said Mass for a crowd estimated by Colombian authorities at just over a million people in Bogota’s sprawling Simon Bolivar Park.

Under a light drizzle, he ended the day as he had begun it, urging Colombians in his homily to put their differences behind them and beware “the darkness of thirst for vengeance”.

Hours earlier, at the start of his first full day in the country, he had told government leaders in the courtyard of the presidential palace that all Colombians should see peace as a long-term commitment and not allow it to be weakened by partisan politics.

Colombians are deeply polarized as they prepare to receive 7,000 former fighters of the FARC guerrilla group into society and aim to repair divisions after a war that killed more than 220,000 people and displaced millions over five decades.

Many Colombians are furious that under the 2016 peace deal, FARC leaders accused of kidnapping and murder will avoid jail and may receive seats in congress as members of a political party.

President Juan Manuel Santos, who attended both events and is the architect of the peace accord, has an approval rating of about 24 percent.

In both speeches, Francis denounced the social inequality that still plagues Colombia, which has extreme poverty in some rural areas.

At the morning event, he told leaders that “just laws” were needed to “resolve the structural causes of poverty that lead to exclusion and violence”, calling social inequality “the root of social ills.”

‘THICK DARKNESS’

In the evening the leader of the world’s Roman Catholics told Colombians huddled on wet fields: “Here, as in other places, there is a thick darkness which threatens and destroys life - the darkness of injustice and social inequality.”

As part of the peace agreement, the government agreed with the Revolutionary Armed Forces of Colombia (FARC) to distribute more land to poor rural communities and to invest and bring development to war-torn areas.

The FARC, which began as a peasant revolt in 1964, has also pledged to help subsistence farmers switch from illegal crops like coca, the raw material that makes cocaine, to food.

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“We want to hear the message of love and peace, so that we open our hearts and leave hatred behind,” said 54-year-old William Soacha, a clothes salesman, waiting with his family under the rain for the pope’s Mass to begin.

The 80-year-old pope, who showed signs of fatigue by Thursday night, has received a tumultuous welcome since his arrival on Wednesday, with his motorcade having to stop or slow down often because of crowds mobbing the ‘popemobile’.

In his speech at the presidential palace, the pope quoted from the 1982 Nobel Prize acceptance speech of Colombian writer Gabriel Garcia Marquez about life and love being the proper response to oppression.

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In an apparent reference to the late author’s best-known work, ‘One Hundred Years of Solitude’, he added:

“There has been too much hatred and vengeance. The solitude of always being at loggerheads has been familiar for decades, and its smell has lingered for a hundred years; we do not want any type of violence whatsoever to restrict or destroy one more life,” he said.

He also prayed in the colonial cathedral before a painting of Our Lady of Chiquinquira, the patron saint of overwhelmingly Catholic Colombia, before addressing a raucous crowd of young people.

He left a message in the cathedral’s visitor book, writing: “I come here as a witness of peace, of the peace that God wants for Colombia. This will be possible with the efforts of all.”

He will visit the cities of Villavicencio, Medellin and Cartagena before leaving for Rome on Sunday night.