Farc is holding hundreds of hostages in jungle camps, either for ransom or to exchange for government-held rebels.

In Madrid, Ingrid Betancourt - held for six years by Farc - appealed for the rebel group to release its captives.

The protests were smaller than ones held earlier this year, when millions marched in support of the hostages.

"We are thinking during these moments of those who are chained to a tree, who live in humiliation, we carry this cross with them and we want to relieve them of these chains," Ms Betancourt said.

"We invite Farc to lay down their arms," she added.

She was rescued along with three American military contractors and 11 Colombian military personnel in a daring rescue operation in July.

Farc defeats

The Farc (Revolutionary Armed Forces of Colombia) has fought to overthrow the Colombian government and install a Marxist government since the 1960s.

In the 1990s it turned to the drug trade to raise money for its struggle and has suffered a series of defeats in recent years, including a number of defections and the Betancourt rescue.

The group holds 28 high-level hostages they hope to trade for hundreds of Farc guerrillas captured by security forces, something the government has ruled out.

Farc is also holding several hundred other hostages it is holding for ransom as a source of funds.

Before Ms Betancourt's rescue, millions of Colombians protested to show their outrage at the hostage situation.

With the reduced size of the protests, it appears that not only has the international community forgotten about Colombia's kidnap victims, but that the ire of Colombians themselves is much diminished, says the BBC's Jeremy McDermott in Bogota.

BBC