Fighters opposed to Yemen's dominant Houthi movement seized four districts in the central province of Ibb on Monday, residents and local officials said, bringing the armed resistance closer to the group's stronghold in the capital Sanaa.
Tribal gunmen and Sunni Islamist militias loyal to Yemen's exiled government took control of the areas amid heavy clashes with the Shi'ite Houthis, in the latest of a series of northward gains with the backing of Gulf Arab air strikes and weapons.
The northernmost district overrun, Al-Radma, is 125 km (80 miles) from Sanaa, which was conquered by the Iran-allied Houthis in September in what they called a revolution against corrupt officials backed by the West.
A political crisis in Yemen descended into civil war in late March when Houthi forces plunged southward toward the main southern port of Aden in late March and caused President Abd-Rabbu Mansour Hadi to flee to Saudi Arabia.
A Saudi-led Arab military coalition began a bombing campaign against the Houthis on March 26 to restore the exiled government and fend off what they see as Iranian influence in their backyard.
The conflict has killed more than 4,000 people and spread hunger and disease in the impoverished nation.
Deadlocked for almost four months, the war has tipped somewhat to the advantage of the Houthis' opponents, with their seizure of Aden last month and advance into nearby areas with the help of tanks and heavy artillery shipped by the United Arab Emirates.
The southern fighters battled Houthi forces on Monday in the southern city of Lawdar, one of the last Houthi strongholds in Abyan province.