The aircraft departed from Pyongyang and was en route to Mehrabad airport in Tehran, the report said. The shipping firm was listed as Korea Mechanical Industry Co.
The movement of North Korean arms to Iran appears to have been an effort to violate UN sanctions against North Korea that was foiled by the Thai government, diplomats said.
Although Iran is subject to separate UN sanctions because of its nuclear programme, it is not forbidden to import arms.
Council diplomats said on condition of anonymity that the sanctions committee was expected to discuss the Thai report next month when it considers its latest quarterly report, due on February 11.
The committee will probably send letters to Pyongyang and Tehran for details on the shipment, the Western diplomats said.
North Korea was hit with fresh UN sanctions last year to punish it for a nuclear test in May 2009, its second atomic detonation. The expanded measures are aimed at cutting off its arms sales, a vital export estimated to earn the destitute state more than $1bn a year.
North Korea's biggest arm sales come from ballistic missiles, with Iran and other Middle Eastern states as customers, according to US government officials.
The UN sanctions and the cut-off of handouts from South Korea have dealt a heavy blow to the North, which has an estimated GDP of $17bn, and may force it back into nuclear disarmament talks in the hopes of winning aid, analysts said.