Colombia says suspected left-wing rebels based in neighbouring Ecuador have carried out more attacks on Colombian farmers.
Foreign Minister Fernando Araujo said no government would stand by with its "hands crossed" while its citizens were killed from across the frontier.
Many Colombian farmers on the border have been destroying coca plants as part of a government-backed initiative.
Mr Araujo called on Ecuador to help co-ordinate border security.
The left-wing Revolutionary Armed Forces of Colombia (Farc) uses the proceeds of the cocaine trade to partly fund its insurgency.
Colombia suspended its coca defumigation programme in the border area after Quito protested about a military raid into Ecuador earlier this month to target Farc rebels.
The raid provoked the worst regional tensions in recent years, with Ecuador breaking off diplomatic relations.
On Tuesday, Colombian President Alvaro Uribe said the government had evidence that an Ecuadorean killed during the raid was linked to the Farc rebel group.
The Ecuadorean foreign ministry said the incident constituted an abuse of human rights.
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