CAIRO — Saudi Arabia said Saturday that its navy had evacuated 86 Arab and Western diplomats from the port city of Aden in southern Yemen, as a Saudi-led coalition conducted a third day of air strikes against the Iranian-backed Houthi movement. The evacuation of the diplomats from Aden reflected the spreading chaos in Yemen as the Houthi-allied forces continued to advance, even under the pressure of the Saudi bombing. Aden is Yemen’s second-largest city and had been the provisional headquarters of President Abed Rabbo Mansour Hadi, the Saudi-backed Yemeni leader, since the Houthi forces overran the capital, Sanaa, in January. [...] the Houthis have also struck an alliance with Yemen’s former strongman, Ali Abdullah Saleh, who retained significant support among the Yemeni military and security forces even after he was forced from power in 2012. The United States is providing intelligence and logistical support for the Saudi-led campaign, including conducting surveillance flights and providing refueling tankers, the Associated Press reported.