Bogota , Colombia ( CNN ) -- Colombian authorities have killed dozens of leftist guerrillas in the past day , the nation 's defense minister said Wednesday . Operations throughout the country led to the killing of 39 suspected members the Revolutionary Armed Forces of Colombia and the capture of a dozen others from the rebel group , Defense Minister Juan Carlos Pinzon told reporters . `` This is one of the greatest blows ( to the rebel group ) in the last five years , '' Pinzon said . One operation near the Venezuelan border led to the killing of 36 suspected rebels and the capture of five others , including a top leader of one faction of the rebel group , he said . The joint military-police operation occurred in the department of Arauca , where over the weekend authorities said rebels killed 11 troops in an attack . The Revolutionary Armed Forces of Colombia , known as the FARC , has been at war with the Colombian government since the 1960s . While severely weakened in recent years , the guerrilla group has continued to carry out kidnappings and attack security forces . A mediator said Wednesday that the FARC will begin releasing its 10 remaining government hostages on Monday . `` With much joy and satisfaction we want to inform you that next Monday the FARC will hand over the 10 uniformed people , police and soldiers , that are in their control , '' said Piedad Cordoba , a former senator who has helped coordinate hostage handovers in the past . The hostage release could take two days , Cordoba said . She did not specify where it would take place . In December , the FARC announced the planned release of six national police officers in the group , but later postponed their release because of an alleged militarization in the area where the rebels operate . Journalist Fernando Ramos contributed to this report .
NEW : A mediator says the rebel group will begin releasing 10 hostages Monday . The rebels have been holding a number of foreign journalists since last week in exchange for their release from captivity. The defense member calls the operation `` one of the greatest blows '' against the rebels . A top leader of one faction of the Revolutionary Armed Forces of Colombia is captured , he says .