A council fighting against Yemen's Houthi rebels said Wednesday that it had expelled the leader of a separatist movement and charged him with treason after he reportedly declined to travel to Saudi Arabia for talks.

The latest upheaval in southern Yemen is revealing a growing divide among the Persian Gulf powers, cracking the coalition fighting the Iran-aligned Houthis. Longstanding differences between Saudi Arabia and the United Arab Emirates — from Sudan to energy policy — have spilled into Yemen, where they back rival factions. The rift has deepened strains between the two neighbors, who officially share the goal of countering the Houthis, in control of the capital, Sanaa, since 2014.