Smoke plumes rose over Saudi Arabia’s capital Saturday after explosions were heard near Riyadh’s King Khalid International Airport, prompting the government to issue air-raid alerts as fighting with Iran-backed Houthi forces in neighboring Yemen escalates.

Saudi Arabia’s Civil Defense issued warnings to residents of Riyadh and the surrounding area early Saturday, telling people to remain indoors because of an aerial threat. The alert was lifted shortly afterward, although authorities urged residents to avoid gathering in crowds. Flames and thick black smoke were later seen rising from a fuel storage area near the airport.