The revolutionaries reportedly advanced into the districts of Mualla and Qalwa'a in Aden on Sunday.
A local official, whose name was not reported, confirmed the Ansarullah fighters’ advance on Mualla, saying they captured the provincial government headquarters, according to Press TV.
Mualla is claimed by militants loyal to fugitive Yemeni President Abd Rabbuh Mansur Hadi, who is now in neighboring Saudi Arabia.
The Ansarullah fighters also targeted a television station loyal to Hadi in Aden, forcing the station off the air.
They fired mortar rounds at the Aden TV building, which was "damaged but there were no casualties," a Yemeni official at the government-run channel told AFP.
The Houthis have been engaged in fierce clashes with al-Qaeda militants and the Hadi government remnants over the past two weeks.