CAIRO/DUBAI: Yemen's Iran-backed Houthi movement launched a series of attacks on southern Saudi Arabia on September 8, hitting four cities and injuring more than 70 people.

The attacks appeared to mark a significant expansion of the six-month-old conflict in the Middle East. Saudi authorities reported that 73 people were injured, including women and children. Fires were also reported at several oil-related sites.

The Houthis said they had carried out a wide-ranging military operation deep inside Saudi territory. They reported using drones and missiles against several targets.

The attacks reportedly included a Saudi military airbase in Khamis Mushait and facilities linked to Saudi Arabia's state-owned oil company near Abha. Other targets were reported in Najran, close to the Yemen border, and Jazan, an important port on the Red Sea.

Saudi authorities confirmed that fires had broken out at some of the targeted locations. The large number of reported injuries suggested that the strikes were among the most serious Houthi attacks on Saudi Arabia since the United States and Israel began their war against Iran in February.

There were no immediately confirmed images showing the damage in the Saudi cities. The Houthis did release images of an explosion involving what they described as Saudi trucks that had been attacked near the border.

The latest strikes came after a relatively quiet period in August. Fighting in the wider Middle East region has since intensified again, with Iran and the United States exchanging attacks. The renewed conflict has also pushed oil prices higher.

Brent crude rose by more than two percent on September 8, moving above US$99 a barrel. Further Houthi attacks on Saudi Arabia could increase pressure on global energy markets because they could threaten oil supplies from the region in addition to the disruption around the Strait of Hormuz.

Saudi Arabia has led an Arab military coalition fighting the Houthis in Yemen for more than 10 years. Although the conflict had become less intense in recent years, a ceasefire has now broken down. The Houthis have also threatened shipping near the entrance to the Red Sea.

Saudi-led coalition spokesperson Colonel Turki al-Malki said the coalition would respond strongly to the attacks.

"The coalition will take all necessary operational measures to deter this terrorist militia and resolutely confront its hostile approach," he said in a statement posted on X.

Houthi spokesperson Yahya Saree accused Saudi Arabia of making the conflict worse by carrying out air strikes against Yemen. He said the Houthi movement would retaliate.

The latest escalation is taking place as the wider Middle East conflict has developed into a confrontation between Washington and Tehran. Both sides are using military and economic pressure to force the other to change course.

The United States is seeking to keep oil moving through the Strait of Hormuz, a key global energy route at the entrance to the Persian Gulf. At the same time, Washington is attempting to restrict Iranian oil exports through a blockade beyond the strait.

Despite US military strikes that have weakened Iran's conventional military capabilities and placed further pressure on its already struggling economy, Tehran still has a large stock of missiles and drones.

Those weapons give Iran the ability to threaten oil tankers traveling through the Strait of Hormuz. Iranian forces have also used missiles and drones to target US military bases across the region.