The Saudi-backed presidential council in Yemen has expelled the leader of a separatist group and charged him with treason after he failed to fly to Riyadh for talks.
Six other members of the presidency accused Aidarous al-Zubaidi, head of the United Arab Emirates-backed Southern Transitional Council (STC), of undermining the independence of the republic.
A Saudi-led military coalition said Zubaidi fled after not joining STC officials on a flight from Aden and moved a large force to al-Dahle province. Coalition aircraft launched strikes on the forces in response, it added.
The STC said the strikes, which reportedly killed four people, were unjustified and that Zubaidi was still in Aden.
It also expressed concern that contact had been lost with the group's delegation in Riyadh.
The past few weeks have seen southern Yemen moving to the brink of a new conflict, pitting factions battling the Iran-backed Houthi movement in the country's decade-long civil war against each other and deepening a rift between Saudi Arabia and the UAE.
STC-aligned forces have in recent years taken control of much of the south, which they want once again to be an independent state, by pushing out forces loyal to the internationally recognised government and the Presidential Leadership Council overseeing it.
In December, the STC's forces launched offensives to seize the eastern provinces of Hadramawt and al-Mahra from the government, saying they were necessary to restore stability in the south and combat the Houthis, al-Qaeda and Islamic State group.
However, Saudi Arabia warned last week that the advances near the kingdom's borders constituted threats to its national security.
It also accused the UAE of pressuring its separatist allies to push into eastern Yemen and expressed support for a demand from the presidential council for all Emirati forces to leave.
At the same time, the Saudi-led coalition struck what it said was a shipment of weapons and military vehicles for the STC that had arrived from the UAE.
The UAE expressed deep regret at the Saudi accusations and denied there were any weapons, but agreed to pull its remaining forces out of the country.
Since then, forces loyal to the government have largely retaken control of Hadramawt and al-Mahra with the help of coalition air strikes.
In order to further diffuse tensions, Zubaidi and an STC delegation had been due to fly from Aden to Riyadh for talks with the government. However, the coalition said the plane left three hours late without Zubaidi, who fled to an unknown location.
Coalition spokesman Maj-Gen Turki al-Malki claimed that Zubaidi had moved a large force towards al-Dhale, prompting pre-emptive strikes aimed at disrupting these forces.
As the situation intensifies, the presidential council issued a decree stripping Zubaidi of his position and referring him for prosecution on serious charges.
The STC has claimed that Zubaidi continues to function as its leader from Aden and expressed shock at the escalation from the coalition, which it viewed as counterproductive to ongoing dialogue efforts.
