SANAA, Yemen — An Iranian airplane delivered supplies to Yemen’s Shiite rebel-held capital on Sunday, while the president gained support from influential tribal and provincial leaders in signs that the rival camps seeking to rule the rapidly unraveling country are entrenching their positions. The first direct flight from Shiite powerhouse Iran to Sanaa was carrying 12 tons of medical supplies as well as tents and Red Crescent aid workers, said Iran’s deputy ambassador Rasai Ebadi. Western embassies shut down and evacuated staff from Sanaa last month after the rebels stormed the presidential palace and placed President Abed Rabbo Mansour Hadi and his Cabinet ministers under house arrest. Hadi received local officials in Aden on Sunday, along with influential tribal leaders and elders from the provinces of Jawf, Marib and Bayda, who assured him of their backing, local television stations reported, adding that Hadi again accused the Houthis of launching a coup against Yemen’s legitimate leadership.