ADEN (Dispatches) – UAE-backed southern Yemeni separatists took control of the port city of Aden after two days of fighting with Saudi-backed mercenaries, residents said Tuesday, confining the regime of former president Abd Rabbuh Mansour Hadi to the presidential palace.
Fighting between the separatists and forces loyal to the Saudi-based Hadi risks crippling their once united military campaign in Yemen, including against the Houthi movement in the country’s north.
Residents said forces loyal to the Southern Transitional Council (STC), formed last year to push for the revival of the former independent state of South Yemen, seized the last stronghold of its Presidential Protection forces rival in Dar Saad area in northern Aden in battles that at times involved heavy artillery and tank fire.
Activists shared photos on social media of the Southern Yemeni flag flying over the base's gate.
The STC is backed by the UAE, a main component of the Saudi-led mercenaries.
Residents said STC fighters from the Southern Resistance Forces had earlier overrun Presidential Protection forces outposts in central Aden's Crater and Tawahi districts.
An International Committee of the Red Cross (ICRC) official said more than 36 people had been killed in the fighting.
Separatists stopped outside the al-Maasheeq palace, where Hadi’s self-declared PM Ahmed bin Daghr's regime is based, residents said.
Saudi Arabia, which intervened in Yemen in 2015 to restore Hadi's regime after he resigned and fled the country, called in a statement on Tuesday on both parties to cease hostilities.
The fighting began on Sunday after a deadline set last week by the STC for Hadi to dismiss bin Daghr's regime, accusing it of corruption and mismanagement, expired.  
Witnesses said UAE-backed elements celebrated the STC victory with fireworks that lit the night skies over Aden. The crowd chanted slogans demanding restoration of the southern state that merged with North Yemen in 1990.
The flare-up has added yet another dimension to one of the world's most complicated conflicts, a war that has left thousands dead and millions on the brink of starvation.
Residents were hunkered down at home as five separatist fighters were killed by snipers and four soldiers died in clashes, military sources said, with tanks and heavy artillery entering the fray.
Aden has served as the headquarters of Hadi's regime since he fled the capital Sanaa three years ago.
Separatists have dispatched additional forces from the central province of Marib and the southern province of Abyan, security sources said.
Saudi Arabia launched airstrikes against Yemen in March 2015 and sent troops to support those loyal to Hadi. Close to 14,000 people have been killed since.
UN envoy to Yemen Ismail Ould Cheikh Ahmed urged all parties to return to "calm and dialogue".
The negotiator is to step down in April after three years overseeing UN-brokered negotiations between Hadi and Houthis, none of which have stemmed the violence.
South Yemen was independent -- with former British colony Aden as its capital -- from its formation in 1967 until 1990, when it was unified with North Yemen.