bogota former marxist farc rebel choose join drug traffic gang instead demobilize face full power colombia military president juan manuel santos say thursday amid worry gang stymie security gain 11,000 fighters collaborators revolutionary arm force colombia farc hand weapons year part peace accord government end five decades war group keep initial reincarnation political party country ombudsman say 800 former guerrillas demobilize figure keep estimate security source think tank put number dissident ex-farc members range 700 1,000. farc leaders renounce dissidents emphasize group move forward peaceful political party go throw everything dissidents santos tell journalists hesitation santos say number dissidents 15 percent fighters say usually refuse demobilize rebel group lay arm peace deal human right group analysts express worry lack state presence territory formerly occupy farc allow small national liberation army eln guerrilla group criminal gang battle control lucrative coca crop illegal mine sit amnesty international say report thursday despite reduction civilian deaths conflict rag several part country presence gang eln farc dissidents face full force colombia military president