"Launching indiscriminate attacks is prohibited by international humanitarian law and can constitute a war crime," said Amnesty's Samah Hadid.

"A high death toll may have been averted, possibly due to the missiles being intercepted, but that doesn't let the Huthi armed group off the hook for this reckless and unlawful act," Hadid said in a statement.

"These missiles cannot be precisely targeted at such distances, so their use in this manner unlawfully endangers civilians."

Amnesty did not say it had independently documented evidence of the attacks.

Saudi Arabia is at the helm of a military coalition that has fought alongside the Yemeni government against the Iran-backed Huthi rebels since 2015.

The coalition said Saudi Arabia's air defence forces had intercepted seven Yemeni rebel missiles late Sunday night, with one Egyptian labourer reported killed by falling shrapnel in Riyadh.

The rebels confirmed they had launched missiles at Riyadh as well as the southern cities of Khamis Mushait, Jizan and Najran.

Both parties in the Yemen conflict have drawn harsh condemnation for failing to protect civilians in a war that has claimed nearly 10,000 lives and pushed the country to the brink of famine.

Amnesty last week said Saudi Arabia and its allies could stand guilty of war crimes in Yemen, which is under partial blockade by the coalition.

The Saudi-led alliance last year landed on a UN blacklist for the killing and maiming of children.