Colombian police say they have foiled a plot by left-wing Farc guerrillas to kidnap the two grown-up sons of President Alvaro Uribe.
President Uribe takes a hardline stance towards Farc
Police chief Oscar Naranjo said 10 people had been arrested after phone calls made by imprisoned guerrillas were monitored.
Reporters heard a tape allegedly recorded in October in which two inmates apparently plan the kidnapping.
Farc is seeking to negotiate a swap of hostages for its own jailed members.
Gen Naranjo said the police had started monitoring the phone calls of three imprisoned leaders of the Farc seven months ago on a tip-off from confidential sources.
"In the perverse mafia logic of the Farc, I imagine they viewed [Uribe's children] as an extremely valuable booty," Gen Naranjo said.
He added police had concluded the elite Teofilo Forero mobile unit of the Farc - the Revolutionary Armed Forces of Colombia - planned to kidnap Tomas Uribe, 26, and Jeronimo Uribe, 24.
Ingrid Betancourt is the most high-profile hostage held by Farc
Gen Naranjo said security for the two president's sons has been reinforced.
Correspondents say this move could further complicate current efforts to exchange hostages held by Farc for members of the guerrilla group in Colombian jails.
French President Nicolas Sarkozy, who has lent his support to mediation efforts, wants to see the Farc release Colombian-French national Ingrid Betancourt - kidnapped while campaigning for the Colombian presidency in 2002.
Last month, Colombia terminated Venezuelan President Hugo Chavez's role as mediator between the government and the rebels.
Farc has been waging a guerrilla war against the Colombian government since the 1960s and is holding scores of politicians, police and soldiers hostage, using them for ransom and political leverage.