SANAA (Reuters) - At least 15 people were killed in heavy fighting between Sunni Muslim tribesmen and Shi'ite Houthi rebels in central Yemen on Friday, increasing fears of outright sectarian warfare.
The Houthi rebels also entered Radaa city, in the central province of al-Bayda, a bastion of the Yemen-based al Qaeda in the Arabian Peninsula (AQAP), local officials and residents said.
The Houthis established themselves as Yemen's new powerbrokers last month, capturing the capital Sanaa on Sept. 21 to little resistance from residents or from the weak administration of President Abd-Rabbu Mansour Hadi.
Their ascendance has angered al Qaeda, which views Shi'ites as heretics and Houthis as pawns of Iran. Last week, AQAP claimed a suicide bombing on a Houthi gathering that killed at least 47 people.
In Friday's fighting, medical sources said 15 people from both sides were killed on the outskirts and inside the city of Ibb, 150 km (90 miles) south of Sanaa.
"We are hearing the sound of machine-guns and mortars everywhere," a resident told Reuters by telephone.
The city of Ibb borders al-Bayda province.
Al Qaeda said in a statement that its fighters had stormed the town of Odein, near Ibb on Wednesday, killing three soldiers and holding it for nine hours before withdrawing.
Houthi fighters have been making advances outside of Sanaa in recent days, taking over cities and towns with the apparent agreement of the authorities there. At least 10 people were killed on Thursday in fighting between Houthi tribesmen and al Qaeda-linked militants.
In addition to the rise of AQAP and the Houthi takeover of Sanaa, Yemen, an impoverished country of 25 million people, faces a secessionist movement in the south. The widespread and growing instability has alarmed neighboring Saudi Arabia, the world's top oil exporter, and other Gulf Arab states.
Western and Gulf Arab countries have supported a U.N.-backed political transition since 2012 led by Hadi and meant to shepherd the country to stability after decades of autocracy.
Reporting by Mohammed Ghobari; Writing by Rania El Gamal; Editing by Gareth Jones