SANAA, Yemen — Ultraconservative Sunni Muslim militants and rebels belonging to a branch of Shiite Islam battled each other in northern Yemen with artillery and machine guns Thursday in clashes that killed more than 40 people, security officials said.
The violence between Islamic Salafi fighters and Hawthi rebels has raged for weeks in Yemen's northern province of Saada, but the latest sectarian clashes marked an expansion of the fighting to the neighboring province of Hagga. The government brokered a cease-fire last month to try to end the violence, but both sides have repeatedly broken the truce.
Officials said Thursday's clashes began when ultraconservative Salafis took over a Hawthi stronghold in a mountainous area near the border with Saudi Arabia. The two sides battled with artillery, mortars and machine guns in the town of Fagga. The officials say that most of the casualties were on the Hawthi side.
The officials said that Salafis, however, accused Hawthis of trying to infiltrate their strongholds in Fagga.
The officials spoke on condition of anonymity because they weren't authorized to discuss the fighting publically.
Hawthi launched in insurgency in 2004 against autocratic President Ali Abdullah Saleh, who stepped down in 2012 after a popular uprising against his rule. Over the course of the Hawthi rebellion, hundreds of people were killed and an estimated 125,000 people uprooted until the rebels and the government struck a fragile cease-fire in 2010.
Under the deal, the rebels agreed to disarm, release captured soldiers and property, clear mountain hideouts and abide by the constitution.
But the north remained restive despite the truce, and fighting flared along another fault line in November after Hawthis accused the Salafis of trying to gain a foothold in their territory by spreading their school of Islam, taking over mosques and winning followers.
Some observers have described the conflict as a proxy war between Iran, the regional Shiite power, and Saudi Arabia, the regional Sunni heavyweight.
Saudi sent its troops in 2009 to put down the Hawthi rebellion after Hawthis killed two Saudi border guards. Some 133 Saudi soldiers died in the fighting with Hawthis, who declared a unilateral cease-fire with Saudi Arabia.
The rebels say their community of Shiite Muslims from the Zaydi sect suffers discrimination and neglect and that the government has allowed ultraconservative Sunni extremists too strong a voice in the country. Hard-line Sunnis consider Shiites heretics.
Some fear that the clashes disrupt the key six-month National Dialogue sessions among representatives from Yemen's rival political, tribal, religious and social groups that aim to reach a consensus over the country's political and economic woes before writing a new constitution and holding elections.
"These clashes are very dangerous," said deputy head of the National Dialogue Yassen Noman.