Debris from missiles fired by Yemen's Houthi rebels into Saudi Arabia caused a small fire on a university campus in the kingdom's south, the Riyadh-led military coalition operating in Yemen said.
Saudi air defence intercepted five ballistic missiles and four drones deployed by Yemeni rebels on Wednesday night and Thursday morning, according to the coalition.
The missiles were fired and drones sent from Yemen's Sa'ada province, a rebel stronghold in the north of the country, toward the Saudi city of Jizan, said coalition spokesman Turki al-Maliki.
"Debris fell on the campus of Jizan University, causing a small fire which was brought under control and there were no casualties," the spokesman said, according to the official Saudi news agency SPA.
Maliki condemned the escalating Houthi air campaign against "civilian targets", warning that these "hostile acts constitute war crimes".
A Houthi spokesman in the northern capital of Sanaa said that 11 missiles and drones had targeted facilities belonging to the Saudi oil giant Aramco.
Patriot anti-missile batteries and other "sensitive facilities" were also targeted by the Houthis in Jizan, a rebel military spokesman said according to the Houthis' Al-Masirah television.
On Monday, the Houthis claimed to have carried out other attacks against Saudi Arabia, saying they had launched 17 drones and missiles at various targets including Aramco facilities.
Saudi authorities did not confirm any attacks on oil facilities at the time. However, the coalition indicated that six drones launched from Yemen had been intercepted, without mentioning any casualties.
Saudi Arabia leads a military coalition that intervened in the Yemen conflict in 2015, to support the the internationally recognised government.
It has reported numerous attacks by the rebels on Aramco facilities, airports and other civilian targets in recent months.