"Strike to ELN: 12 of its members neutralized in (the province of) Arauca. Congratulations to the army. The offensive will continue to bring peace," Santos wrote on his Twitter account yesterday.
Soldiers took the two injured rebels into custody.
The ELN, Colombia's second-largest guerrilla group, has about 2,500 fighters.
In August, the government said it was ready to start negotiating with the group, nearly a year after talks began with the larger FARC rebel force, potentially broadening the peace process aimed at ending Latin America's oldest insurgency.
