RIYADH — The Royal Saudi Air Force and Royal Saudi Air Defense destroyed a number of Houthi drones targeting civilian airports in the Kingdom, Saudi Press Agency (SPA) reported on Monday. Arab coalition spokesperson Col. Turki Al-Maliki said the militants had started carrying out simultaneous attacks as part of their terrorist tactics. Similar tactics were used in Aden on Thursday, Aug. 1, when a military parade was targeted killing 11 people, with the assistance of a Daesh affiliate. Al-Maliki said attacks which target civilians are a breach of international humanitarian law and are considered a war crime and he said the coalition would continue fighting the Houthis, which he said was legal under international law. The Iran-aligned Houthi rebels' Al-Masirah television earlier said their drones targeted civilian airports in the southern cities of Abha and Najran as well as King Khaled airbase in Khamis Mushayt. The strikes come just days after the rebels carried out a deadly attack on a security training camp near Yemen's government-held second city Aden. The rebels said they launched a drone and a ballistic missile at the camp. The Houthi rebels have stepped up missile and drone attacks across the border in recent weeks. Nine civilians were wounded in a July 3 Houthi attack on Abha airport, the coalition said. A June 12 missile attack on the same airport wounded 26 civilians, drawing warnings of "stern action" from the coalition. And on June 23, a rebel attack on Abha airport killed a Syrian and wounded 21 other civilians, the coalition said. The raids come amid heightened regional tensions as key Saudi ally the United States presses a "maximum pressure" campaign against its arch-rival Iran after withdrawing from a landmark 2015 nuclear deal between major powers and Tehran. Saudi Arabia has repeatedly accused Iran of supplying sophisticated weapons to the Houthis, a charge Tehran denies.