Bogota, July 13 -- Peace remains elusive in many parts of Colombia nearly three years into the implementation of the nation's historic peace accord with leftist rebels. But a leader of a U.N. Security Council mission says the world body remains firmly behind it.

Peruvian U.N. Ambassador Gustavo Meza Cuadra spoke after the team met President Ivan Duque Friday to kick off a visit to Colombia to assess the accord's progress at a time of mounting concern.

Vast rural territories once controlled by rebels are now in the hands of illegal armed groups, while alarming numbers of social leaders are being killed.

Ambassadors on the council will meet with political leaders and visit a transition zone where rebels are making the shift to civilian l...