Their report describes how parts of shipments from Uganda and Djibouti, including rocket launchers, grenades and ammunition could not be accounted for.
The pro-government fighters were reportedly supported by artillery, rocket launchers and tanks. The spy says Russia was kept informed about the coalition response.
The Defense Department says the package includes additional ammunition for US-provided HIMARS rocket launchers, additional howitzers, artillery and mortar rounds, and anti-armor capabilities.
State media in North Korea say the country's leader Kim Jong-un ordered and oversaw the testing of rocket launchers and short-range tactical guided weapons fired on Saturday.