Some army officers, rebel groups and criminal networks in Congo are still illegally exploiting the country's gold and mineral riches despite government and military bans, U.N. experts said in a report circulated Monday. The panel of experts monitoring sanctions against Congo said gold remains by far the mineral most used to finance rebel and criminal groups. It names several senior officers implicated in gold exploitation and trade, “on occasion in collaboration with private companies.'' The report to the U.N. Security Council said a gold-tracing program has not yet become operational and efforts for the government to control its natural resources are impeded by "the impunity enjoyed by wrongdoers,'' corruption by a wide range of parties, and loopholes in implementing bans and monitoring. Rebel groups using children It noted violations of human rights and international humanitarian law, citing the continuing use of children by rebel groups in eastern Congo and "killings, kidnapping and destruction of property" in the Beni and Rutshuru areas of the eastern province of North Kivu. The experts also accused South Sudan's opposition leader and former vice president, Riek Machar, of entering Congo with military equipment last August in violation of the arms embargo against all non-government groups. Machar was fleeing fighting with South Sudan forces loyal to President Salva Kiir that erupted in the capital, Juba. On the key issue of Congo's vast natural resources, the panel said its preliminary investigations showed that "most gold produced in the country continued to be smuggled through neighboring countries to Dubai, United Arab Emirates." Recommendations ignored The report said the UAE has worked with the experts but “unfortunately” the panel's recommendations to Burundi, Uganda and the UAE to tackle the smuggling and reduce the quantity of gold illegally exported and sold in those countries have not been implemented. The experts said they were aware Congo's army began investigating three generals and two colonels in South Kivu in September for their alleged involvement in gold exploitation and two of the officers were suspended. While this was welcome, the report said, a senior army officer involved in the process told the experts in November “that the investigations had already ended and that there would be no prosecution.” The experts expressed concern that “a failure by the Congolese authorities to prosecute would maintain a cycle of impunity” and undermine efforts to end the involvement of army officers in exploiting natural resources. Congo urged to prosecute In comparison with gold, the experts said, rebels have had fewer opportunities to interfere in the supply chain of three other valuable minerals — tin, tantalum and tungsten — but it cited a case of an armed group still earning money from these minerals. The experts also said armed groups in Congo receive only “minimal financing” from ivory poaching, with the most revenue going to foreign groups. The panel called on Congo's government to investigate and prosecute military officers allegedly involved in natural resources exploitation, to continue investigating the South Kivu officers, and to comply with mining regulations.