On March 25, the Iran-backed rebels fired seven ballistic missiles into Saudi Arabia.

Saudi authorities said their defences intercepted all seven, but falling debris from one of the missiles killed a migrant worker in the capital Riyadh.

Human Rights Watch said the missile attacks "violated the laws of war" as they were fired "indiscriminately at populated areas", calling on the Huthis to cease their attacks.

Over the weekend, Saudi air defences intercepted another Huthi missile targeting the southern city of Najran.

The Yemen war -- which has created what the UN has called the world's largest humanitarian crisis -- has killed nearly 10,000 people since 2015, when a regional military coalition led by Saudi Arabia joined the government's war against the rebels.

While both parties in the war stand accused of neglecting civilian safety, the Saudi-led coalition in particular has drawn harsh condemnation from international rights groups for civilian deaths, landing on a UN blacklist last year for the killing and maiming of children.

The Huthis have intensified missile attacks on Saudi Arabia since November, and the coalition imposed a blockade on Yemen ports and airports in retaliation.

The blockade has since been partially lifted.

"The Huthis should immediately stop their indiscriminate missile attacks on populated areas of Saudi Arabia," said Sarah Leah Whitson, Middle East director at Human Rights Watch.

"But just as unlawful coalition airstrikes don't justify the Huthis' indiscriminate attacks, the Saudis can't use Huthi rockets to justify impeding life-saving goods for Yemen's civilian population."