The ceasefire brings to an end the group’s 52-year-old war, one of the world’s longest insurgencies, after four years of peace talks in Cuba.
The final peace agreement will be signed in the next few weeks.
“I order all our commanders and units and each one of our combatants to definitively cease fire and hostilities against the Colombian state from midnight tonight,”
Timochenko told reporters.
Colombian President Juan Manuel Santos signed a decree earlier to halt military operations against the Farc, also from midnight.
“The end of the conflict has arrived!”
he said in a tweet on Friday.