Hundreds of thousands of Colombians wearing white T-shirts marched in their homeland and abroad Monday to demand the country's largest rebel group stop kidnapping people and release those it holds.

The idea of the protests against the Revolutionary Armed Forces of Colombia, known as the FARC, was born less than a month ago on the social networking Web site Facebook, and nearly 100,000 people in 165 cities around the world confirmed their participation.

The protests were concentrated in Colombia and Latin American capitals, though there were smaller protests in other places including Sweden, Hungary, France, Italy and India.

Long lines of people shouting "Freedom! Freedom!" marched along the main throughfare of the Colombian capital. Television channels suspended normal programming to broadcast marches around the country, and anchors wore white T-shirts.

Crowd estimates in Colombia varied wildly, with estimates at the Bogota march ranging from 500,000 to 2 million.

"I hope the FARC is listening," said former hostage Clara Rojas, who took part in the march. She was freed last month after nearly six years in captivity.

Colombia's government says the FARC is holding more than 700 hostages, including three U.S. military contractors and former French-Colombian presidential candidate Ingrid Betancourt, whom it is trying to swap for imprisoned rebels. Talks brokered by Venezuelan President Hugo Chavez recently led to the release of two hostages, including Rojas.

The FARC have called the march an attempt to bolster the political fortunes of its enemy, President Alvaro Uribe.

"If the suffering of those in captivity has been unjustifiably prolonged ... this has been because of the inhuman intransigence and worthless pride of President Uribe," rebel leaders said in a statement released Friday.

Uribe addressed a packed public square in the northeastern city of Valledupar on Monday.

"To our fellow countrymen who live abroad, and who today have united with the rest of their compatriots, we want to extend our gratitude," he said.

In neighboring Venezuela, more than 2,000 people wearing white T-shirts marched in Caracas. In Panama, hundreds of Colombians demonstrated, while some 400 people shouted anti-FARC slogans in Argentina. In Mexico City, about 200 people gathered in front of the Angel of Independence monument.

In Stockholm, protesters bowed their heads for a minute of silence, while a couple dozen people in Hungary protested for an hour outside parliament. Television images showed Colombians and Americans at rallies in Washington, New York and Miami. Others joined events in Paris, London and Madrid.

Inside Colombia, the mobilization has exposed deep divisions over how to end the decades-long conflict that preceded the nation's cocaine wars, Latin America's oldest and strongest leftist insurgency.

For weeks, invitations to the march flew through cyberspace, mainly among the young and relatively wealthy who use Facebook in a country where about one in four can afford to use the Internet regularly. But as momentum grew, so did criticism of the march's narrow focus.

Many relatives of hostages fear the protests could endanger their loved ones, while others argue the march should denounce all violent groups, including the far-right militias critics say are backed by politicians in Uribe's camp.

On Saturday, Colombian news organizations received a statement from the rebels promising to release three more ailing hostages. No date was set.