Yemeni separatists backed by the United Arab Emirates (UAE) on Tuesday seized the area around the presidential palace in the southern city of Aden, following fierce battles with forces loyal to the internationally-backed government, security officials said.

The battle for the government's de-facto capital — which erupted on Sunday — has left at least 36 people dead, and has exposed deep divisions in the Saudi-led alliance fighting against Iran-backed Houthi rebels, who control much of northern Yemen, including the real capital Sanaa.

Read more: Yemeni president calls for ceasefire in Aden

What's the latest

• Witnesses described seeing celebrations as forces loyal to the Southern Transitional Council (STC) — who want to revive the former independent state of South Yemen — fought all the way to the gates of the al-Maasheeq palace in Aden, where Prime Minister Ahmed bin Dahar's cabinet is based.

• Hours earlier, STC fighters — who are backed by the UAE — seized a key presidential security base in the north of the city.

• Prime Minister Ahmed bin Dahar and several ministers were expected to flee to neighboring Saudi Arabia following the latest action, but it was unclear if they had done so.

• Global charity Save the Children said it has suspended its humanitarian work in Aden out of fear for the safety of its staff. 

Read more: Yemen's forgotten war: Locals tell their stories

Calls to end hostilities

The Saudi-led coalition, which intervened in Yemen's civil war in 2015 to restore President Abed Rabbo Mansour Hadi's government from the Iran-backed Houthis, called on both parties to cease hostilities.

"The coalition will take all the measures it deems necessary to restore stability and security in Aden," it said in a statement on Tuesday.

The US, which backs the Saudi-led coalition, also called on all parties to "refrain from escalation and further bloodshed," according to a State Department statement.

Yemeni President Hadi, who has been in exile in Saudi Arabia for most of the country's multi-fronted civil war, has described the separatists' capture of the city as a "coup."

Read more: German ban on arms exports to Yemen conflict called into question

How does this development fit into the main conflict in Yemen: The seizure of Aden opens yet another front in the country's devastating civil war. The main conflict between the Hadi-Saudi alliance and the Houthis rebels has been in a bloody stalemate for three years. 

Last month, the Houthi's own alliance with forces loyal to former president Ali Abdullah Saleh broke apart after Saleh switched sides to the Saudi coalition after becoming frustrated with the Houthi's monopoly of the north. Saleh was killed and his fighters and loyalists were overrun and arrested. 

The civil war is further complicated by the presence of al-Qaida and the "Islamic State" (IS) militant group, who are ready to take advantage of any power vacuum.

When did fighting in Aden start: The fighting broke out in Aden on Sunday, when a deadline issued by the separatists for the government to resign expired. The clashes started when government forces prevented rallies by the STC from taking place.

Why has this happened: Hadi and the UAE, which are both part of the Saudi-led coalition, have been locked in a long-running power struggle. Hadi has accused the UAE of taking advantage of Yemen's civil war to boost its own influence in the south of the country.

The UAE is also suspicious of his alliance with the Yemeni branch of the Muslim Brotherhood, a pan-Arab political movement that the Emirates views as a terrorist organization. 

Read more: Saudi Arabia gives Yemen $2 billion to stave off hunger and prop up currency

How could this play out: Some analysts think the potential split in the coalition could threaten Yemen's territorial integrity.

Read more:Top UN mediator for Yemen steps down

mm/aw (AP, Reuters)