Yemen’s government agreed a truce with rebels led by Abdel Malek Al-Houthi in February to halt a war that has raged on and off since 2004 and displaced 250,000 people. The cease-fire has largely held, but unrest has risen in recent weeks.

Rebels and tribal sources gave conflicting accounts of Thursday’s clash, highlighting the confusion that has long surrounded the conflict in the Saada area of north Yemen.

“The Houthis opened fire on a position of the central security forces, who responded in kind,” a Yemeni tribal source said of the gunbattle, adding that three rebels were killed.