BOGOTA, Aug 10 (Reuters) - At least 18,667 children in Colombia were forced to join the now-demobilized FARC guerrilla group and subjected to abuses and treatment considered war crimes over a 20-year period, the country"s transitional justice court (JEP) said on Tuesday. The JEP"s investigation, which will see 26 former members of the Revolutionary Armed Forces of Colombia (FARC) called to testify, relates to case 07, which concerns the former rebel group"s recruitment and use of minors. Children were used in many ways by the FARC as part of a systematic policy that was systematically implemented, JEP magistrate Eduardo Frentes said at a press conference. "A provisional estimate, which could be even greater, of 18,667 boys and girls used in the conflict by the FARC is, without a single doubt, one of the most terrible acts that could have happened during the conflict," he said. The tally came from analyzing 31 data bases compiled by victims groups and the state, as well as testimonies from 274 people who were forcibly recruited, said Lily Rueda, the JEP magistrate leading case 07. As the investigation - which focused on the recruitment of minors between 1996 and 2016 - advances, the JEP will also look at associated sexual and gender-based violence, and forced disappearances, as well as murder, torture, and cruel and degrading treatment. Elsewhere in Colombia underage children continue to be used by other illegal armed groups, who use them as fighters, human shields, and sex slaves, according to the government. The numbers published by the JEP are far above those previously released by the government, which had estimated that more than 7,400 minors were recruited in Colombia between 1985 and 2020, while 16,000 died during the conflict. The JEP was created under a 2016 peace deal to prosecute former FARC rebels and military leaders for alleged war crimes and has the power to impose lighter sentences than the ordinary justice system. Former FARC leaders, who have since formed a political party called Comunes, were not immediately available to comment, but have previously said recruitment of minors was not a general policy and that many joined the rebels" ranks for protection or to escape poverty.