Colombia's FARC rebels have said they would pay reparations to victims of the country's long war under a recent peace accord.

Until now, the guerrillas had said they did not have money to pay damages because everything went to their war effort.

Eight youths left FARC rebel camps in Colombia on Saturday, as the insurgents began relocating children and teenagers as part of a historic peace agreement, the Red Cross said Saturday.

The government of President Juan Manuel Santos and the Marxist guerrillas of the Revolutionary Armed Forces of Colombia (FARC), the country's largest rebel group, concluded a final peace accord last month to end a 52-year war. 

The United Nations will coordinate some 500 international observers to verify that FARC rebels comply with a ceasefire and surrender weapons once a peace deal is signed, Colombia's Congress said Wednesday.

The Colombian government and the Marxist Revolutionary Armed Forces of Colombia (FARC) are in the final phase of four years of talks that it is hoped will result in a peace deal putting to an end a half-a-century of conflict.

Venezuela will temporarily re-open its border with Colombia on Sunday, a state governor said, a move that will allow desperate Venezuelans to stock up on food, medicine and other basics sorely lacking in their country.

"We will not put up any obstacle... whoever wants to cross can cross," Jose Vielma Mora, governor of the border state of Tachira, told reporters Thursday.

Five hundred hungry Venezuelan women rushed across a bridge into Colombia in defiance of a year-long border closure in search of basic foods and commodities that have grown scarce at home due to a crippling economic crisis.

The women, dressed mostly in white and coming from towns in western Tachira state, managed to break through a military cordon, across a bridge and into the northeastern Colombian city of Cucuta.

Colombia's FARC guerrillas urged another rebel force to release a missing journalist, a rare gesture of support for the government over the sensitive issue of kidnappings as a peace deal nears.

The leader of the Revolutionary Armed Forces of Colombia (FARC), Timoleon Jimenez, called on the rival leftist National Liberation Army to free Salud Hernandez, a Spanish-Colombian reporter.

A journalist who has been missing in northeast Colombia appears to have been kidnapped by a leftist guerrilla group, the Spanish foreign minister and newspaper for which she works said Monday.

"The Spanish journalist and El Mundo correspondent in Colombia, Salud Hernandez-Mora, has been detained by guerrillas," the Spanish daily announced online, citing Colombian military sources and saying she disappeared in the Catatumbo region. She was last seen on Saturday.

Colombia's second-largest guerrilla group, the National Liberation Army (ELN), freed an ex-governor on Sunday held captive since 2013, in a new boost to peace efforts.

"Pleased by the release of (Choco department) ex governor Patrocinio Sanchez Montes de Oca. Much support to him and family. #welcometofreedom," the Choco governor's office said on Twitter.

Colombia's second-largest guerrilla group, the National Liberation Army (ELN), freed a policeman on Saturday after holding him captive for 13 days, in a boost to peace efforts.

The government launched peace negotiations on Wednesday with the ELN, setting its sights on a total end to a bloody half-century conflict.

Tens of thousands of people protested in more than 20 cities across Colombia on Saturday against President Juan Manuel Santos and his government's peace process with the FARC guerrillas.

The demonstrations come just days after Bogota launched peace talks with the country's second-biggest guerrilla group, the National Liberation Army (ELN), setting its sights on a total end to a bloody half-century conflict.