Two soldiers and two civilians were killed and 44 others wounded after Houhti militants and supporters of former Yemeni president Ali Abdullah Saleh shelled areas in Ta'iz city in the early hours of Friday.
The clashes continue between army and resistance forces and Hothis militants north and east of the city.
The army forces killed 7 militants and injured 12 others in the clashes, a military spokesman in Ta'iz Mansour Al-Hasani said.
The Arab coalition's planes shelled sites of Houthi, west of Ta'iz.
The situation in Yemen worsened when Houthis and soldiers loyal to Ali Abdullah Saleh, the former Yemeni president, swept across southern Yemen, taking the port city of Aden and forcing the Arab Gulf-backed President Abd Rabbu Mansour Hadi into exile.