Yemen's former President Ali Abdullah Saleh gestures as he arrives to a rally in Sanaa. (Khaled Abdullah/Reuters) The violent conflict engulfing Yemen, the Arab world's poorest country, intensified on Saturday, as Houthi rebels fought government forces for control of Aden, a crucial port city. Meanwhile, air strikes launched by a Saudi Arabia-led coalition attacked Houthi positions in an attempt to repel the group that now controls most of Yemen.