Iran complained to the United Nations Security Council of the Saudi Arabia-led coalition's forces hindering its attempts to send aid to Yemen as a standoff loomed on Wednesday over an Iranian cargo ship bound for the Arabian Peninsula under military escort.

Gulf Arab nations in the military coalition have since March 26 been bombing Houthi militia and allied army units that control much of Yemen as well as inspecting ships in a bid to stop weapons smuggling.

Iran said on Wednesday it would not allow coalition forces to inspect the humanitarian shipment, which is being escorted by Iranian warships. Saudi Arabia has accused Tehran of arming the Houthis, charges the Islamic Republic denies.

"The Islamic Republic of Iran has tried by all means to alleviate the suffering of the affected Yemeni people; efforts that have mostly been thwarted by the coalition forces," Iran's U.N. Ambassador Gholamali Khoshroo wrote to the Security Council in a letter sent late on Tuesday and seen by Reuters.

"Indeed, the destruction of the transportation infrastructure of Yemen by the coalition forces has adversely impacted the delivery of humanitarian assistance," he wrote.

A five-day truce that began on Tuesday to allow for the delivery of aid to Yemen appeared to be broadly holding. The United Nations says some 12 million people in the war-torn impoverished country need help.

The United States has urged Tehran to redirect its ship to Djibouti, from where the United Nations is coordinating aid distribution. Iran's state news agency IRNA said the vessel left on Monday for a Yemeni port held by Houthis.

Khoshroo said that "those who violate international law, including international humanitarian law, should be held accountable for their acts and there should be no room for impunity."

Saudi Arabia and its Sunni Muslim allies believe the Houthis are a proxy for the influence of their regional rival, Shi'ite Iran, in a power struggle that has helped exacerbate sectarian tensions across the Middle East.

In a statement on Tuesday, the U.N. Security Council called on all parties to respect the five-day humanitarian pause.

It "urged all parties to allow for the entry and delivery of essential relief items to the civilian population ... and to facilitate the field activities of humanitarian agencies, in coordination with the government of Yemen."

By Reuters