Three people were killed when a gunfight broke out in northern Yemen, rebels and tribal sources said Thursday, in the latest outbreak of violence that threatens to undermine a two-month-old truce. 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. Yemen warned rebels Thursday against violating the truce and taking up arms against the government again, after leaflets were distributed calling for ‘jihad,' the Interior Ministry said. The ministry expressed concern over the leaflets distributed by Zaidi rebels calling for ‘holy war,' the ministry website said without giving details. The rebels, also known as Houthis, distributed the leaflets after leaders met in the small town of Bart Al-Anan in the northern province of Al-Jawf near to their strongholds in Saada, the ministry said. Security services in Al-Jawf warned the Houthis from “playing with fire” and called on to them to commit to the “six-point truce” that led to the Feb. 12 ceasefire after six months of fighting. 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, adding that three rebels were killed.