Sanaa, Yemen: Even as scores of people were killed in heavy fighting between government loyalists and rebels for control of Yemen's third city, Taiz, Yemeni residents said al-Qaeda was moving into a vacuum in newly "liberated" areas.

Saudi-backed government forces have made sweeping gains in Taiz, seen as crucial gateway to the rebel-held capital Sanaa. But factions within the coalition organised by the Saudis have also been turning against one another, sometimes with gunfire, as they pursue starkly different visions of Yemen's future.

Militants loyal to Yemen's exiled government ride a tank they seized from Houthi militiamen in Taiz. Credit:Reuters

The Iran-backed Houthi rebels have been driven from large swaths of southern Yemen over the past several weeks, but little thought appears to have been given to securing the new areas.