SANAA — Two Yemeni soldiers were killed and two wounded when they were ambushed while on patrol by suspected al-Qaeda militants in the central province of Marib, a regional official said on Thursday.

Marib has most of Yemen’s oil and gas fields and has long been a battleground between various factions, including local tribesmen, Al-Qaeda in the Arabian Peninsula (AQAP) insurgents and other Islamists, and government forces.

Now tribesmen say the province is subject to an advance by Iranian-allied Houthi fighters, who took over the capital Sanaa in September and brought about the collapse of the U.S.-backed government last week.

A CIA drone strike on a car in Yemen killed three suspected al Qaeda militants in Marib on Monday, the first since the Sanaa government stepped down, in a sign such U.S. operations will continue despite the political crisis.

Houthi leader Abdel-Malek al-Houthi said on Tuesday his movement was seeking a peaceful transfer of power after the resignation of President Abd-Rabbu Mansour Hadi and urged all Yemeni factions to work together to that end.