Five policemen were killed in the overnight offensive by militants on the town of Udain, 20 kilometres west of the now rebel-controlled Ibb, the security official and local sources said.
The gunmen attacked the police headquarters, which was set ablaze, and the offices of the local government, as well as the post office.
Al-Qaeda is active in several Yemeni provinces, mainly in the south and southeast, where repeated government military campaigns drove the network's militants out of key cities they once controlled.
Already in control of Sanaa and the strategic port city of Hudeida, the rebels yesterday appeared to have taken control of the Dhamar and Ibb provinces, security officials said.
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Just as in Sanaa and Hudeida, the rebels faced no opposition as they entered the two provinces and set up checkpoints, the officials said.
The rebels have been taking advantage of a power vacuum in Yemen to seize control of significant areas, threatening the authority of the Sunni-led central government.
Deadly fighting broke out Tuesday when the Huthis tried to expand out of the town of Rada in central Baida and clashed with Al-Qaeda militants.
Five rebels, six suspected Al-Qaeda militants and a civilian were killed during the fighting in Rada, a security official and tribal sources said yesterday.
Impoverished Yemen, a key ally in US efforts to combat Al-Qaeda, has been wracked by political turmoil and sporadic violence since an uprising toppled strongman Ali Abdullah Saleh in 2012.