Waving flags and wearing white T-shirts printed with "No more kidnapping, No more lies, No more killing, No more FARC," protesters streamed out of offices and homes as the rally snaked through Bogota to the Andean capital's main plaza.
Recent videos showing hostages chained up and despondent after as long as a decade in captivity have fueled outrage against the FARC, which the United States and Europe brand a terrorist group funded by Colombia's cocaine trade.
"No more FARC, we don't want any more FARC, young people have to say no to the FARC and tell them to stop their violence," said Jaime Martinez, a student wrapped in a Colombian flag and with "Peace" painted on his face.
Violence from Colombia's conflict has ebbed under President Alvaro Uribe, a Washington ally who has used billions of dollars in U.S. aid to counter Latin America's oldest insurgency and the country's drug traffickers.
But the FARC is still holding 44 key hostages, including French-Colombian politician Ingrid Betancourt and three Americans, it wants to exchange for jailed rebels. Officials say the rebels hold around 700 more captives for extortion.
Guerrilla hostages are now at the center of a dispute between Colombia and Venezuela's anti-U.S. president, Hugo Chavez, over his role in brokering the release of captives.
Before the march, the FARC announced it would hand three of its hostages to Chavez, who in January negotiated the release of two other captives. But his call for the FARC to be removed from terrorism lists has fueled tensions with Colombia.
"We have already started making contacts and movements," Chavez said in Caracas, without giving a time-frame for the hostage rescue operation.
FROM SYDNEY TO BOGOTA
Local television showed images of hundreds of Colombians braving freezing weather to march in Japan and expatriates gathered to protest in cities in the United States, Australia, Europe and South America.
Blowing whistles and chanting anti-FARC slogans, protesters packed into Bogota's Bolivar Plaza, where large images of hostages were draped from the mayor's building. Images taken from helicopters over the city showed the rally filling parts of a major highway.
The idea for the march originally came from a campaign by a group of students on the social networking Web site Facebook, where they called their protest a "Million Voices against the
But the demonstration has underscored political divisions in Colombia. Supporters and opponents of Uribe accused each other of trying to score political points. Hostage families also expressed worries about retaliation against captives.
Critics say the protest should have been against all armed groups, including paramilitaries accused of carrying out massacres in the name of counterinsurgency before they disarmed under a peace deal with Uribe.
Uribe is popular for his security crackdown, which has helped make cities and highways safer. But he faces criticism over a scandal tying some of his lawmaker allies to former commanders of the now-demobilized paramilitaries.
Attempts to reach a hostage deal are deadlocked over a rebel demand that Uribe demilitarize an area the size of New York City in southern Colombia. He has refused, saying that would allow the FARC to regroup, but has offered a smaller zone under international observation.