Warships from the US Navy and allied nations have intercepted four weapons shipments from Iran to war-ravaged Yemen since April 2015, a US admiral said Thursday.

Yemen has been rocked by conflict since Iran-backed Huthi rebels overran the capital Sanaa and other large parts of the country in 2014, prompting military intervention by a Saudi-led coalition in March last year in support of the internationally recognised government.

The United States and Saudi Arabia have accused Iran of arming the insurgents, and while Tehran denies the charges, the coalition has since enforced maritime and air controls over the Arabian Peninsula country.

"Either US ships or coalition ships... intercepted four weapons shipments from Iran to Yemen," said US Vice Admiral Kevin Donegan.

"We know they came from Iran and we know the destination," he told reporters at an undisclosed military base in Southwest Asia.

Donegal said the shipments contained thousands of AK-47 assault rifles, anti-tank missiles, sniper rifles and "other pieces of other equipment, higher-end weapons systems".

Naval officials were able to determine the destination of the boats' by analysing GPS settings and interviewing the crew.

One of the shipments had been validated by the United Nations as being an illegal weapons shipment, said Donegal.

His comments come after the US military's Central Command chief General Joseph Votel said last week Iran may have played a role in suspected Huthi missile attacks this month against US warships in the Red Sea.

"We believe that Iran is connected to this in some way," Donegan said.

Given the heavy volume of traffic around the Strait of Hormuz and the Gulf, the three-star admiral said "plenty" of other shipments would have gone through to Yemen.

The arms seizures came after Iran in April 2015 tried in vain to send a convoy of seven ships, guarded by two Iranian Revolutionary Guard Corps vessels, to Yemen.

The Shiite Huthi rebels are believed to be behind this month's attacks in which surface-to-surface missiles were fired at the USS Mason on at least two occasions.

In response, US cruise missiles on October 13 struck Huthi radar sites.

The Mason and two other warships were likely targeted in a third missile attack on October 15, but officials have not conclusively confirmed what the threat was or where it was coming from.

- Peace roadmap -

Yemen's conflict has killed nearly 7,000 people, wounded more than 35,000 and displaced at least three million since the Saudi-led coalition launched military operations, according to the United Nations.

The UN special envoy to Yemen Ismail, Ould Cheikh Ahmed, submitted to the rebels in Sanaa on Tuesday a proposal to revive a political process.

The contents have not been made public.

But informed sources say the roadmap calls for agreement on naming a new vice president after the rebels withdraw from the capital Sanaa and other cities, and hand over heavy weapons to a third party.

President Abedrabbo Mansour Hadi would then transfer power to the vice president who would appoint a new prime minister to form a government in which the north and south of Yemen would have equal representation.

The government has remained non-committal, saying it has not received any roadmap for a political settlement.