BOGOTA (Reuters) - The United Nations mission charged with overseeing Colombia’s peace accord with former FARC rebels said on Thursday that six ex-guerrilla commanders were failing to fulfill their obligations under the deal and had left reintegration camps.

The Revolutionary Armed Forces of Colombia (FARC) signed an accord in late 2016 to end more than 52 years of war with the government. It is now a political party that uses the same acronym.

The UN Verification Mission is charged with managing two dozen zones around the country where former fighters can live and take part in reintegration projects.

Most fighters were given amnesty and financial help under the deal, but commanders are expected to be tried at a special tribunal for alleged war crimes and human rights violations and to serve alternative sentences if convicted.

In recent weeks, six former commanders in the country’s southeast “took the decision to leave the zones and abandon their responsibilities to approximately 1,500 ex-combatants who live there,” the UN said in a statement.

“Despite the leaders’ departure, the ex-combatants and their families continue to live, study and work there, committed to the reincorporation process,” it added. “Independent of what motivated the ex-commanders to take this decision, they are failing to fulfill their obligation.”

The six missing commanders include Hernan Dario Velasquez, known as by his nom de guerre El Paisa, and Henry Castellanos, known as Romana, a source who works at an organization that closely follows the peace process said.

Velasquez was convicted in absentia for ordering the 2003 bombing of an upscale club in Bogota that killed 36 people. Castellanos is alleged to have been involved in drug trafficking and well-known kidnappings during his time in the FARC.

The other commanders’ noms de guerre are Ivan Ali, Albeiro Cordoba, Enrique Marulanda and El Zarco Aldinever, the source said.

The FARC political party did not immediately respond to a request for comment.

A spokeswoman for the government high peace commission said it had no comment yet.