Saudi Arabia has deployed more troops in southern Yemen to try to contain clashes between nominal allies in the Saudi-led military coalition fighting the Houthis that risk further fragmenting the country.
The fight for the south of the country has opened a new conflict, focused around the port of Aden, in a multifaceted war that has killed tens of thousands and pushed the long-impoverished Arabian Peninsula nation to the brink of famine.
Saudi soldiers and armed vehicles arrived over the weekend in the capital of the oil-producing Shabwa province where the United Arab Emirates-backed separatists have been battling forces of Yemen's Saudi-backed government for control, two local officials said.
The two sides are part of the Sunni Muslim coalition, led by Saudi Arabia and the UAE, that intervened in Yemen in March 2015 against the Iran-aligned Houthi group which ousted the government of Abd-Rabbu Mansour Hadi from power in the capital Sanaa in 2014.
But the separatists, who seek to restore the former South Yemen republic, turned on the government in early August and seized control of Aden, interim seat of Hadi's government.
They have since been trying to extend their reach to nearby Abyan and Shabwa, clashing repeatedly with government forces.
Saudi Arabia has reinforced its positions in Shabwa and Aden as Riyadh called for talks to resolve the crisis and refocus the Western-backed coalition on battling the Houthis, who have stepped up missile and drone attacks on Saudi cities.
"Saudi forces arrived in Shabwa and started working with the local government for a de-escalation and a ceasefire. All parties responded positively to the coalition's calls," coalition spokesman Colonel Turki al-Malki said on Monday.
The kingdom has also called for a summit in Jeddah to defuse the standoff. On Tuesday, leader of the UAE-backed Southern Transitional Council (STC), Aidarous al-Zubaidi, arrived in the Saudi Red Sea city on Tuesday to meet Yemeni and Saudi officials, a spokesman of the movement said.
TRENCHES AND TUNNELS
Saudi Arabia's main coalition partner, Gulf ally the UAE, openly intervened on behalf of the STC last week by bombing government forces trying to regain control of Aden, forcing them to retreat.
STC forces also brought reinforcements into Aden, witnesses said on Tuesday, calling back fighters who had been deployed on the outskirts of the main port of Hodeidah, held by the Houthis, in the west.
The fighters dug tunnels and built trenches at the edges of Aden and blocked main roads leading out of the city to prevent government forces from recapturing it, they said.
The STC, which accuses Hadi's government of mismanagement, made its move on Aden after the UAE scaled down its military presence in Yemen in June under increased Western pressure to the end the war.
Escalating violence across Yemen and the evident rift between Saudi Arabia and the UAE could complicate U.N. efforts to restart peace talks to end the conflict, which is largely seen as a proxy war between Saudi Arabia and Iran.
Earlier this week, coalition warplanes bombed a prison complex in southwest Yemen, killing more than 100 people. The United Nations called for an investigation but the coalition insisted it had struck a Houthi arms storage site.
A member of a U.N. panel of independent human rights experts on Yemen expressed concern on Tuesday about the fighting in the south.
"This again causes us concern in that the parties to the conflict themselves seem incapable of even agreeing amongst themselves as to the way forward," Charles Garraway said.
The panel also said the United States, Britain and France may be complicit in war crimes in Yemen by arming and providing intelligence and logistics support to the Saudi-led coalition that it said starved civilians as a tactic of war.
Its report accused the anti-Houthi coalition of killing civilians in air strikes and deliberately denying them food in a country facing famine. It said the Houthis, for their part, had shelled cities, deployed child soldiers and used "siege-like warfare".
Neither the Saudi government communications office nor UAE officials responded immediately to Reuters requests for comment.