Sept 9 (Reuters) - Saudi Arabia's Civil Defense lifted an alert it had announced in the southern city of Khamis Mushait on Wednesday, a day after Houthi attacks there and in three other nearby cities wounded 73 people and set oil installations ablaze.Yemen's Iran-aligned Houthis struck an airbase in Khamis Mushait and oil infrastructure in the nearby cities on Tuesday in one of the biggest attacks in Saudi Arabia since the start of the U.S.-Israeli war on Iran in February.Saudi authorities did not provide details for the reasons behind Wednesday's alert in Khamis Mushait.

Fires erupt at several sites; senior Saudi air force officer vows coalition will respond firmly to attacks; Houthis say they will soon make statement about large-scale op

The Iranian-backed Houthi rebels in Yemen have launched attacks on Saudi Arabia, wounding over 70 people and igniting fires at oil facilities