SANAA, Yemen (AP) -- Shiite Houthi rebels fired mortars and rockets into the central city of Taiz on Wednesday, killing at least 17 civilians and wounding over 70, including women, children, and the elderly, officials said.

Taiz, Yemen's third-largest city, is besieged by the rebels, who are blocking deliveries of food, water and medicine. Witnesses, who spoke on condition of anonymity for fear of retribution, say the shells landed in residential areas, and that fighting was preventing ambulances from reaching the wounded.

One witness, Mohammed Hazza, said that the dead in Taiz lay scattered in the streets, some torn to pieces.

The officials, who are neutral in a conflict that has split the armed forces, say Saudi-led warplanes struck Houthi positions including the city's presidential palace, while clashes raged on the outskirts of Taiz. At least seven Houthi-allied fighters were killed, they added, speaking on condition of anonymity because they were not authorized to brief the media.

Yemen's fighting pits the Houthis and allied army units against forces loyal to the coalition-backed government as well as southern separatists and other militants. The Saudi-led air campaign began in March.