Pro-government tribes battled Shiite rebels north of the Yemeni capital on Wednesday taking the death toll from three days of heavy clashes to 38, tribal and medical sources said.
The deadliest fighting raged in the Arhab region just 40 kilometres (25 miles) north of Sanaa, where tribesmen said they had recaptured high ground overlooking the international airport.
The rebels have been pushing out from their stronghold in the mountains of the far north to other areas nearer the capital, where most of the population follow the Zaidi branch of Shiite Islam, to lay a stake to their own autonomous unit in a promised federal Yemen, political sources say.
But their fighters, know as Huthis from the name of the rebels' leading family, have faced stiff resistance from pro-government Zaidi tribes, as well as from Sunni hardliners from elsewhere in Yemen who have established religious schools in parts of the north.
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"The men of the Arhab tribe pushed the Huthis back from Mount Nisr and three adjacent hills in fighting that erupted on Tuesday evening, inflicting 10 dead in Huthi ranks and at the cost of seven dead among our own men," a tribal spokesman said.
A little farther north in Omran, which borders Sanaa province, fighting between the rebels and pro-government tribesmen on Wednesday left nine people dead, tribal and medical sources said.
President Abdrabuh Mansur Hadi has pledged that Yemen will adopt a federal constitution to tackle the grievances of its disparate regions.
But at a ceremony on Saturday to mark the conclusion of a troubled 10-month national dialogue, he put off any decision on the thorny issue of how many component units it will have, promising that a special commission will decide.
The prospect of a federal Yemen, originally mooted as a solution to the grievances of the formerly independent south where secessionist violence has been on the increase, has spawned demands for autonomy from other discontented regions, including the rebel-held far north.