UNITED NATIONS (AP) — The U.N. envoy for Colombia called Wednesday for improved protection for former combatants who continue to be killed “in alarming numbers,” and he complained of rising violence and massacres by other groups that have cropped up since the 2016 peace accord.

Carlos Ruiz Massieu told the U.N. Security Council that efforts must also be stepped up to fight impunity for these crimes, “including by bringing intellectual authors to justice.”

“Priority should be given to staffing and resources for the National Protection Unit to clear the backlog of pending requests for protection for former combatants,” he said.

Secretary-General Antonio Guterres’ latest report to the council, circulated last week, said the U.N. political mission in Colombia verified 19 killings of former combatants from the country’s main rebel group, the Revolutionary Armed Forces of Colombia (FARC), in the three-month period ending Sept. 25.

The latest victims included one of the highest-ranking former FARC commanders, Jorge Iván Ramos, who became a FARC political party leader and was killed Aug. 28. The U.N. chief said Ramos was actively engaged in implementing the 2016 peace deal with the government, including working on a crop substitution program and the handover process for FARC assets.

The FARC party addressed an open letter to the National Liberation Army, known by its Spanish acronym ELN, which is one of Colombia’s last remaining rebel groups, expressing shock “over information that ELN was behind the crime,” Guterres said.

He said the latest killings bring the total number of former combatants killed so far this year to 50, including two women. Since the peace agreement was signed, he said, the U.N. mission has verified 297 attacks on former FARC fighters, including 224 killings, 20 disappearances and 53 attempted homicides.

Before the peace deal was signed with the FARC, more than 50 years of war in Colombia caused over 220,000 deaths and displaced nearly 6 million people. An amnesty law was adopted covering most offenses committed by FARC fighters.

Ruiz Massieu told the Security Council that the FARC's laying down of arms and its transition into a political party has been completed and is “irreversible.” But he said the reintegration of FARC members into civilian life, “the search for truth, reparations and restorative justice for victims” and the transformation of rural Colombia remain enormous challenges.

“Despite continued attacks and stigmatization against them, the vast majority of those who laid down their weapons remain engaged in the reintegration process, with nearly a third of them having received funding for productive projects through mechanisms created by the peace agreement,” he said.

But Ruiz Massieu said land for the former combatants continues to be “one of the most pressing matters” for reintegration.

He said the FARC’s decision to disarm “has contributed significantly to the overall reduction of violence since the signing of the peace agreement.”

“Unfortunately," he added, “some of the areas that suffered immensely during the conflict continue to be besieged by violence from other actors who continue attacking social leaders, human rights defenders, former combatants and entire communities. Recent massacres in various departments have served as a painful reminder of how innocent civilians, including young people, are falling victim to the actions of these groups.”

Colombia’s Foreign Minister Claudia Blum told the council “safety and security of former combatants, human rights defenders and social and political leaders remain our greatest challenge.”

She said the government is strengthening prevention and protection efforts and the attorney general has advanced investigations into 126 cases of attacks on ex-combatants, and so far 30 people have been convicted.

Blum called on the U.N. mission to address the FARC’s “lack of contribution to truth, reparations and justice.”

“Colombia demands members of the FARC political party to tell the truth and to recognize their responsibility regarding the recruitment of children, kidnappings, sex crimes, attacks against civilians, planting of anti-personnel mines and forced disappearances among other serious crimes,” Blum said. “Likewise, they must give details on drug trafficking groups, money laundering, and the link between the former guerrilla and other criminal organizations.”