President Juan Manuel Santos led Colombians in a massive march for peace Tuesday, calling for an end to decades of armed conflict at a time when peace talks in Havana are under fire from his predecessor Alvaro Uribe.

Hundreds of soldiers joined Santos and his cabinet ministers at the Plaza of the Fallen Heroes, one of seven starting points for the march by thousands of people, many of them in white T-shirts and carrying white flags.

"We have to end this nightmare of 65 years," said Santos, referring to the 1948 assassination of liberal leader Jorge Eliecer Gaitan, which ignited a long period of political unrest known as "La Violencia."

"Peace is the victory of any soldier. Peace is the victory of any policeman. If we reconcile, we will have a better homeland," Santos said.

Santos then set out on a march through Bogota, wearing a T-shirt with the message: "What matters is to believe. I believe in peace."

An estimated 150,000 people took part, waving white banners and wearing T-shirts that read: "We are the generation of peace."

Santos has opened peace talks with the FARC, a leftist guerrilla group founded in 1964 that grew out of the lawlessness and ideological divisions that also spawned right-wing paramilitary groups and drug trafficking organizations.

But Santos' peace overtures have encountered stiff resistance from Uribe, a conservative hardliner who sought to destroy the FARC militarily during his 2002-2010 presidency, in which Santos served as defense minister.

On Monday, Santos accused his former boss of trying to sabotage the peace talks by disclosing on his Twitter account precise locations where rebel leaders were to leave Colombia for Havana under a military safe conduct.

Most political parties and a variety of civic organizations support the peace march, but Uribe denounced it as "legitimizing the terrorism of the FARC."

The leftist Democratic Pole also has refused to endorse the march, seeing it as a vehicle for Santos' reelection in 2014.

But some of its leaders were taking part, and the FARC sent a message on Monday saluting "each and every person who has decided to march for peace in Colombia."

Bells were rung in churches across the country at noon as marchers converged on Bogota's central Plaza Bolivar. White banners and balloons draped from windows of downtown buildings.

A concert and a reading of "A prayer for peace" by Colombian writer William Ospina were planned. Marches also were organized in other Colombian cities.

Over half a century of armed conflict in Colombia is estimated to have left 600,0000 dead, 15,000 missing, and 3.7 million people displaced by fighting.

"In my region we suffer from violence on the part of the guerrillas and common criminals," said Vianey Leon, a 28-year-old who traveled to Bogota for the demonstration from the central province of Tolima.

"We do not know if we will achieve peace, because the future is uncertain, but that is our hope," she told AFP.

Elizabeth Velez, a 60-year-old homemaker, said she had not directly experienced violence "but it shrivels the heart to see so much suffering."

"I came for the peace of our country, so that even if we don't achieve it, our children will," she said.