Yemen's Iran-backed Huthi rebels said Thursday they fired a ballistic missile at Saudi Arabia and hit a military target, in the second such attack this month, after threatening to retaliate over a crippling blockade.

"We confirm the success of our ballistic missile trial, which hit its military target inside Saudi Arabia," the Huthi-run Al-Masira television channel said.

A spokesman for the Saudi-led military coalition fighting the Shiite Huthi rebels in Yemen did not immediately respond to a request for comment.

Hours earlier in a speech broadcast on Al-Masira, rebel chief Abdulmalik al-Huthi warned against "prolonging the blockade" imposed on Yemen following a November 4 rebel missile attack that was intercepted near Riyadh international airport.

"Should the blockade continue, we know what (targets) would cause great pain and how to reach them," he said.

Saudi Arabia and its allies tightened the longstanding blockade on Yemen's ports and the main international airport in Sanaa in the wake of the November missile attack.

The move prompted the Huthis to warn that they considered "airports, ports, border crossings and areas of any importance" in Saudi Arabia, as well as its ally the United Arab Emirates, legitimate targets.

"We will not stand idly by -- we will seek more radical means to prevent both the tightening of the blockade and all acts aimed at starving and humiliating the people of Yemen," the rebels' political office said this month.

Riyadh accuses its arch-rival Iran of arming Yemen's Huthis and earlier this month Saudi Arabia's powerful Crown Prince Mohammed bin Salman said this "could be considered an act of war".

Saudi Arabia has accused Iran of supplying the Huthis with arms.

Iran's foreign ministry has denied the accusation.

- Rebel rift -

The Huthis, a northern minority that has long complained of marginalisation, descended on the capital Sanaa from their mountainous region in September 2014, seizing the city with little resistance.

Security forces loyal to former president Ali Abdullah Saleh, who ruled Yemen for decades until he resigned under pressure in 2012, joined forces with the Huthis.

Together they forced the government of President Abedrabbo Mansour to flee to the main southern city of Aden and later to Riyadh.

Saudi Arabia and a coalition of mainly Sunni Arab allies launched air strikes in March 2015 against the Huthis and later sent ground troops to support pro-government forces.

The conflict has claimed more than 8,600 lives since the Saudi-led coalition joined the government's war against the rebel alliance.

More than 2,000 people have also died of cholera this year.

The United Nations has warned Yemen faces mass famine unless the Saudi-led coalition allows more food aid into the country, long the poorest in the region.

The coalition allowed limited supplies into select areas in Yemen last weekend.

Yemen's conflict, which has enabled Al-Qaeda in the Arabian Peninsula, or AQAP, and the Islamic State group to flourish in the chaos of war, shows no sign of waning.

The Huthi-Saleh rebel alliance has also begun to unravel, with clashes between the Huthis and fighters loyal to the former president leaving at least 14 dead on Wednesday.

Violence between the two, whose alliance first began to show cracks in August, flared again on Thursday night, localised in southern Sanaa and around the residence of two of Saleh's nephews.