Pope Francis landed in Colombia on Wednesday to plead for lasting peace in a country moving towards the end of a half-century war, and praying for stability in its crisis-stricken neighbor Venezuela.

The 80-year-old Argentine pontiff descended the steps of his plane at a military airport in Bogota and was greeted by Colombian President Juan Manuel Santos and a crowd waving white handkerchiefs.

His visit comes two days after Colombia's government and the country's last active guerrilla group, the ELN, announced a ceasefire, a key step toward sealing a what Santos calls a "complete peace" to end Latin America's longest civil war.

"Peace is what Colombia has sought for a long time, and she is working to achieve it: a stable and lasting peace, so that we see and treat each other as brothers and not as enemies," the pope said in a video message on Monday.

But his first statements after starting the trip concerned Venezuela, where a political and economic crisis has caused food shortages, deadly unrest and calls for President Nicolas Maduro to quit.

As his plane entered Venezuelan airspace, the pontiff issued a telegram -- a traditional gesture for every country he flies over on his apostolic trips.

He sent "cordial greetings" to Maduro and the Venezuelan people, "praying that all in the nation may promote paths of solidarity, justice and concord."

'Pope, help Venezuela'

Authorities say thousands of Venezuelans have fled to Colombian territory to escape the crisis.

Francine Howard, Colombia coordinator for major Venezuelan opposition party Popular Will, said her compatriots would attend the pope's public masses with signs reading "Pope, help Venezuela."

They want Francis to support their calls for a humanitarian corridor from Venezuela to Colombia.

But with respect to Francis's visit, "there is one thing that has made Venezuelans uncomfortable, and that is the call for dialogue," she warned.

"That is hard to accept when you are dealing with a narco-state and a genocidal regime," she said, referring to Maduro's government.

Vatican mediation

As well as trying to mediate in the Venezuelan crisis, Francis has supported recent steps towards peace in Colombia.

His five-day tour will see him meet people who have suffered on various sides in Latin America's longest conflict.

On the flight, Francis told journalists the trip was "a bit special" because it aims to help Colombia "move forward on the road to peace."

The Colombian conflict has left 260,000 people confirmed dead, 60,000 unaccounted for and seven million displaced.

Testimony from survivors, fighters

In Bogota, Colombians lined the streets to welcome Francis, waving red, blue and yellow Colombian flags with his face.

Vendors were selling badges, placards and flags inscribed with the message: "We want peace."

Military police in green fatigues and white belts lined the route Francis was due to take in his Popemobile from the military airport where he landed to the papal mission, the Nunciatura, in central Bogota.

Vatican experts said Francis would be walking a diplomatic tightrope on the trip between calls for justice and mercy.

Santos won a Nobel Peace Prize last year for his work on an accord that led to the disarmament of Colombia's biggest guerrilla group, the FARC. But critics say the rebels are getting off too lightly.

Colombians narrowly rejected the peace deal in a referendum last year.

Francis tried unsuccessfully to mediate between Santos and the lead opponent of the accord, conservative leader Alvaro Uribe.

A reworked version was later pushed through Congress.

"I am in pope mode, and I invite all Colombians to get in pope mode," Santos said on Twitter on Wednesday.

"Let us reconcile and leave behind hatred and vengeance."

Conflict victims

Francis is making his 20th foreign trip as pope and fifth to his native Latin America.

On Thursday he will meet with Santos and leaders of the Catholic Church in Venezuela who have been attempting to help mediate in their country's crisis.

He will then make daily excursions by plane to the cities of Villavicencio, Medellin and Cartagena.

In Villavicencio, he will beatify two Catholic priests killed during the conflict.

He will later preside over a prayer for national reconciliation with victims of violence, former guerrilla members and ex-military fighters.