The Saudi-led coalition and Iran-backed Houthis traded strikes Sunday as fighting raged in the intensifying conflict that has disturbed life for residents of the kingdom's capital Riyadh and war-wracked Yemen.Disruption in the world's top crude oil exporter has continued to spread as the Houthis keep up their strikes, with Riyadh's landmark Kingdom Centre skyscraper ordering "mandatory" remote working until further notice for office tenants.No reason was given for the order, but it follows a security alert and two drone interceptions around the capital on top of waves of Houthi attacks on Saudi targets in recent weeks.Meanwhile, the Saudi-led coalition backing the internationally recognised government has launched repeated air raids on Houthi-controlled regions of Yemen.An alleged Saudi airstrike Sunday in northern Yemen's Saada governorate killed at least nine people and wounded 16 others, the Houthis' Saba news agency reported.The coalition meanwhile said that two pilots were killed when their helicopter crashed in Najran near the Yemen border, while the Houthis said they "downed an Apache helicopter belonging to the Saudi enemy" in the same area.The coalition blamed a "technical malfunction" for the incident, which inflicted its first military fatalities since the long-running war with the Houthis reignited in July.Schools in the Saudi capital and surrounding areas also extended online learning into a second week, while Riyadh's King Khalid International Airport remains closed after 13 people were killed in a major attack last week.The Saudi coalition's decade-plus war with the Iran-backed Houthis has returned with ferocity during the US-Iran war, with regular attacks reported by both sides.Sunday Egypt's parliament postponed a vote on President Abdel Fattah al-Sisi's request to authorise military support for Saudi Arabia, two lawmakers told AFP, extending deliberations today.And Iran's newly appointed Defence Minister Mehrdad Akhlaghi threatened to inflict "enormous damage" on the United States and its allies if Washington resumes its military campaign.Tenants of the Kingdom Centre, which towers over central Riyadh, include financial services giant Merril Lynch, management consultancy McKinsey and the International Monetary Fund."Please be advised that remote working arrangements are mandatory for all office employees at Kingdom Centre, effective immediately and until further notice," the building's management said in an e-mail seen by AFP.The mall at the foot of the building remains open.After an uneasy, four-year truce, Yemen's conflict has surged back to life and intensified when the group seized strategic territory along the Red Sea coast last month.The Houthis have hit Saudi targets including tankers in the Red Sea, oil facilities and Riyadh's King Khalid International airport.A Houthi projectile injured at least six people in southern Saudi Arabia Sunday after it struck a residential area in Najran near the border with Yemen, according to the kingdom's civil defence agency.The coalition also said two ballistic missiles were intercepted in the kingdom's south. Threat alerts for Najran city and As Sulayyil governorate in Riyadh province were issued but quickly cancelled.The Houthis have declared a maritime blockade on Saudi Arabia and captured territory around the Bab al-Mandab strait, the Red Sea chokepoint and vital export route for Saudi oil since Iran blockaded the Gulf's Strait of Hormuz.The hostilities were the focus of a meeting Sunday between the Russian and Saudi foreign ministers on the sidelines of a summit between Gulf states and Russia in Bahrain's Manama.They discussed "regional developments, particularly the escalation in Yemen, as well as the persistent threats to shipping in the Straits of Hormuz and Bab al-Mandab", the Saudi foreign ministry said on X.Saudi Arabia's defence minister, Khalid bin Salman, also wrote on X that he met with UAE President Mohamed bin Zayed al-Nahyan, with the two discussing regional developments.