ADEN, Yemen - Two Yemeni soldiers were killed and two wounded when they were ambushed while on patrol by suspected al-Qaida 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- Qaida 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 US-backed government last week. A CIA drone strike on a car in Yemen killed three suspected al-Qaida militants in Marib on Monday, the first since the Sanaa government stepped down, in a sign such US 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.