The today's seizure comes a day after the rebels, known as Houthis, called for a general mobilisation against forces loyal to the embattled current president, Abed Rabbo Mansour Hadi.
Hadi had just given a defiant speech challenging the Houthis, his first public address since fleeing the capital and establishing a base in the southern city of Aden last month.
Brig Gen Hamoud al-Harathi, commander of special forces units based in Taiz, rejected Hadi's legitimacy as president. Meanwhile, thousands demonstrated in Taiz against both the Houthis and Saleh.