Saudi Arabia accused Iran of supplying weapons to Shi'ite rebels in Yemen and urged the UN Security Council to impose sanctions on Tehran for violating an arms embargo.

Saudi Ambassador Abdallah Al-Mouallimi said in a letter to the council obtained late Saturday by The Associated Press that the smuggling of arms to Houthi rebels violates council resolutions and constitutes "a direct and tangible threat" to Saudi Arabia, Yemen, the region and international peace.

Sunni-majority Saudi Arabia and Shi'ite-majority Iran are regional rivals and back opposing sides in Yemen and Syria.

In Yemen, a Saudi-led coalition backing the internationally recognized government launched a bombing campaign in March 2015 against Iranian-backed rebels known as Houthis who are allied with army units loyal to a former president.

Bombing by the U.S.-backed coalition, comprising nine Arab nations, has pushed the Houthis out of southern Yemen but they still control the capital, Sanaa, which they seized in 2014.

Al-Mouallimi cited several examples of the seizure of Iranian weapons shipments at sea by the U.S., Australia and France. He said the Houthis and forces loyal to Yemen's former president "must be held accountable for their continued irresponsible and criminal behavior."

He urged the council "to take all necessary measures" — diplomatic language for sanctions — to demand that Iran complies with UN resolutions.

Iran's UN Mission "categorically" rejected the allegations, saying the claims have not been independently verified.

The Iranian mission accused Saudi Arabia of waging an "irrational war against the people of Yemen" and cited "numerous confirmed reports documenting Saudi Arabia's war crimes and violation of international law and international humanitarian law."

"It is surprising that Saudi Arabia would complain to the United Nations about the use of weapons in Yemen even while Saudi Arabia itself has purchased tens of billions in arms that it is using against the Yemeni people," the mission said in a statement.

Saudi Arabia and Iran severed diplomatic relations in January after Riyadh executed a prominent Shi'ite cleric and angry Iranian crowds overran Saudi diplomatic missions.

This latest dispute comes as the UN special envoy to Yemen, Ismael Ould Cheikh Ahmed, is trying again to halt the fighting which has killed more than 9,000 people and displaced 2.4 million, and negotiate a political solution. He has stressed that a new cessation of hostilities is key to restarting talks to end the civil war in the Arab world's poorest country.

In the letter dated September 14, Al-Mouallimi reiterated Saudi Arabia's support for Cheikh Ahmed's efforts to end the conflict.

The statement from Iran's UN Mission said, "Iran does not believe in a military solution in Yemen and has always urged for cessation of hostilities, dialogue and resort to legal and peaceful mechanisms to achieve a peaceful resolution to this conflict."

Yemen is expected to be the focus of a meeting on the sidelines of this week's annual meeting of world leaders at the UN General Assembly.