SANAA, Yemen (AP) — Yemen's Shiite Houthi rebels have driven pro-government troops out of the southern Bayda province on Friday, after two months of heavy clashes that killed 550 fighters from the two sides, security and medical officials said.

The Houthis recaptured a key military base in the town of Mukayris and pushed pro-government troops back to Abyan province further south, the officials added. Of the 300 pro-government fighters killed, 30 were mistakenly targeted by airstrikes from the Saudi-led coalition backing the government, they said.

Yemen has been at war for over a year, with Houthis and allied army units battling forces loyal to the internationally recognized government as well as southern separatists and other militants. The Saudi-led coalition has been striking the rebels since March.

Also Friday, Saudi airstrikes killed nine rebel fighters in the Red Sea port of Mocha, part of a renewed attempt to cut rebel supply lines to heavily contested Taiz, security officials said.

The country's third-largest city is in government hands, but is besieged by the rebels. Securing Taiz would allow pro-government forces to push north toward the rebel-held capital, Sanaa.

Taiz is also the capital of a southern province of the same name, where ground fighting Friday killed at least three civilians and 34 fighters from the two sides, security officials said.

Earlier in the day, Saudi airstrikes killed 12 Houthis in the massive desert province of Jawf, paving the way for pro-government ground troops. The move is part of a plan to seize the northern province in order to advance on neighboring Sadaa province — the Houthi heartland.

All officials remain neutral in the conflict, which has splintered Yemen. They spoke on condition of anonymity because they are not authorized to brief reporters.