The Saudi-led coalition fighting in Yemen on Tuesday called for an immediate ceasefire in Aden as supporters of the secessionist Southern Transitional Council surrounded the presidential palace.
More than 36 people were killed and 185 injured in clashes between forces aligned with the STC and government troops over the weekend, according to the International Committee of the Red Cross.
Heavy fighting had intensified overnight in Aden, which is serving as the internationally recognised government's interim capital.
"The coalition renews its call to all parties to ceasefire immediately and end all forms of armed conflict," said a statement from the Saudi-led coalition, which also includes the UAE, carried by the state-run Saudi Press Agency.
"The coalition affirms that it will take all necessary measures to restore security and stability in Aden.”
The coalition — which is fighting in Yemen against Houthi rebels on behalf of the government — said it regretted that the two parties did not respond to its earlier calls for restraint and calm.
“The coalition has regretfully monitored in the past two days parties’ lack of response to calls for calm and restraint,” it said.
“The coalition asks Yemenis to focus on the main goals, in particular the restoration of the legitimate government, the protection of the state, and the restoration of security and stability.”
On Sunday, Minister of State for Foreign Affairs, Dr Anwar Gargash tweeted that “the UAE’s position on the events in South Yemen is clear and principled in its support for the Arab coalition led by Saudi Arabia. No consolation for those who seek division.”
Brig Saleh Al Sayyed, who heads troops that have fought alongside the secessionists since Sunday, said his forces had seized control of the Fourth Brigade, the presidential guard in Aden.
The southern city has served as the government's de facto capital since 2014, when the Houthi rebels seized control of Sanaa in an attempt to overthrow the government of president Abdrabu Mansur Hadi.
Read more: Clashes resume after brief ceasefire in Aden
Formerly independent states, North and South Yemen were unified in 1991 under the presidency of Ali Abdullah Saleh, who was killed in Sanaa in December by the Iran-backed Houthis after he broke his alliance with them. The rebels control most of northern Yemen, and the south is home to the Southern Transitional Council.
Meanwhile, 14 soldiers were killed in southern Yemen on Tuesday in an attack carried out by militants affiliated with Al Qaeda, a military source told The National.
The attack began when a suicide bomber driving an explosives-rigged car struck a checkpoint manned by special operations forces in Ataq, capital of the oil-rich province of Shabwa.
Another car then arrived on the scene carrying gunmen who shot at soldiers manning the checkpoint.
Terrorist networks, including Al Qaeda in the Arabian Peninsula (AQAP) and ISIL, have tried to expand their presence in Yemen.
On Tuesday, UAE armed forces destroyed two military vehicles belonging to the Houthi rebels in Al Hodeidah province's Haiys district.
The first strike destroyed a large amount of weapons and the second killed “dozens” of Houthis, reported UAE state news agency Wam.