The mountainous province close to Yemen's border with Saudi Arabia has been at the heart of a conflict with the government by members of the Zaidi community, a branch of Shia Islam.
The rebel group - called "Huthis" after their late leader Hussein Badr Eddin al-Huthi - is fighting to restore Yemen's Zaidi imamate, which ruled for hundreds of years before being overthrown in 1962.
Thousands of people have been killed in clashes since fighting began in 2004.
Friday's clashes came a day after a team of Qatari mediators returned to Sanaa in a fresh bid to help the two sides reach a deal over implementing the peace accords.
Yemeni authorities and Huthi negotiators have had repeated disagreements over the interpretation of some of the peace deals' clauses.