Saudi Arabia has threatened to retaliate after a wave of Houthi missile strikes set oil facilities ablaze and wounded dozens of people, in what is being described as the Iran-backed group's heaviest attack in years.

Saudi authorities said the strikes injured 73 people, including women and children. The attacks targeted civilian and economic sites in the country's south.

The assault comes after a four-year truce between Saudi Arabia and the Houthis collapsed in July, months into the broader conflict between the United States and Iran in the Middle East.

Fighting in Yemen has intensified in the wake of the strikes, as regional tensions continue to rise.