Yemeni security and tribal officials say at least 25 people were killed in clashes between Sunni tribesmen affiliated to the country's Muslim Brotherhood group and Shiite rebels in a northern city.

The officials said Monday that the killings took place over the past 24 hours in fighting between the Shiite rebels, known as Hawthis, and their rivals in the city of Jawf.

The officials spoke on condition of anonymity because they were not authorized to speak to the press.

The Hawthis, already in control of the northern city of Saada, have been staging demonstrations in the capital Sanaa demanding a new government. The group waged a six-year insurgency that ended with a cease-fire in 2010, and critics have portrayed the demonstrations as part of a power grab.