Two people died in the blasts and six soldiers providing them with protection were injured in the attack, which occurred during an operation targeting coca plants, the leaves of which are used in the production of cocaine.
The donkeys died in the attack.
The workers were reportedly moving between fields when the bombs detonated, probably by remote control.
The deaths were the latest in an ongoing struggle against drug barons, who will often take violent action to protect their drug crops.
Marxist rebels, who fund themselves through drug sales, are believed to be behind the latest attack, which occurred in the Norte de Santander State, northeast of Bogota.