Fuel is being shipped illegally from Iran to Houthi militias in Yemen to finance their war against the government, according to a report by a UN panel of experts seen by AFP.
The findings are expected to again raise questions about Iran's support for the Houthis in the war.
In its final report for 2018, the panel said it had "identified a small number of companies, both within Yemen and outside, which operated as front companies," using fake documents to conceal fuel donations.
The fuel was "for the benefit of a listed individual" who is on a UN sanctions blacklist, it added.
"The revenue from the sale of this fuel was used to finance the Houthi war effort," said the 85-page report sent to the Security Council.
The panel found that the "fuel was loaded from ports in the Islamic Republic of Iran under false documentation" to avoid UN inspections of the cargo, it added.
The experts have in past reports pointed to a possible Iranian link to missiles fired by Houthi rebels at Saudi Arabia, after they traveled to Riyadh to examine weapons debris.
In a previous report, the experts said they were investigating monthly fuel donations from Iran valued at $30 million.
Iran has repeatedly denied that it is providing military support to the Houthis.
The experts also said the Arab Coalition backing Yemen’s government made “significant progress” against the Houthis in 2018.
At the same time, the experts said “the Houthi leadership has continued to consolidate its hold over government and non-government institutions.”