Heavy fighting broke out between government forces and the southern separatist groups Monday in Aden after a brief ceasefire fell apart.
The clashes saw six Southern Transitional Council supporters killed and many more injured in the skirmishes that erupted in a populated district of the interim capital.
The fighting comes as thousands of protesters flocked to Aden to voice their disapproval of the current administration and demand president Abdrabu Mansur Hadi sack his cabinet led by prime minister Ahmed bin Dagher.
Clashes between Yemeni separatists and government units in Aden appeared to have subsided early on Monday after a weekend of deadly battles.
The fighting began on Sunday after the presidential guard prevented a protest demanding the government roll back a decision banning public gatherings in the interim capital.
The Saudi-led coalition, which is supporting the internationally-recognised government of Mr Hadi, called for the ceasefire and urged both sides to focus on the fight against the Iran-backed Houthi rebels.
Protesters insist the calm is not an indication of an abandoned cause and said rallies will continue until their demands are met.
”We will keep protesting in this square until the president takes serious steps to change the current government which drove us to the brink of famine" said Ahmed Al Babakri, a citizen from Shabwah province who came to Aden to support the Southern Transitional Council (STC).
The STC, an autonomous body not recognised by the government and aimed at overseeing self-governance in southern provinces, organised the protests.
The fighting on Sunday spread to other areas of the city including Hadeed mountain, the government headquarters and the shore.
"Thousands of people from all over the southern provinces are gathering in the liberty square in Khourmaksar city, demanding the dismissal of the government which is accused of being complicit in corruption deals," said Mr Al Babakri.
The non-governmental body issued a statement agreeing to the ceasefire set by the Arab coalition but urged its supporters to continue with demonstrations.
"The government holds the responsibility of flaming the clashes up with the civilians who came to Aden from all over the South to protest peacefully," the statement said.
The call for Mr Bin Dagher and his ministers to resign is being led by Aidarous Al Zubaidi, a former governor of Aden province who became head of the STC after being fired by Mr Hadi last year.
"We pledge to keep struggling peacefully and we confirm again that we are committed to the ceasefire of the Arab Coalition," the statement said.
Reports from International Committee of the Red Cross (ICRC) said the fighting ensued overnight in Aden.
"All night shooting in Aden #Yemen, including heavy weapons," Alexandre Faite, the head of the ICRC delegation in the country based in Sanaa, said on Twitter.
"Those in southern part of city, including (ICRC staff) still unable to get out."
The fighting killed 15 people including three civilians, after separatist protesters were prevented from entering the city for a rally to demand the government's ouster from Aden.
Mr Hadi's forces, backed by the Saudi-led coalition that includes the UAE, have recently made steady advances against the Houthi rebels, who still control large parts of Yemen's north including the capital, Sanaa.
Meanwhile, ambassadors sitting on the United Nations Security Council are expected to arrive in Riyadh to inspect the debris from missiles fired by Houthi rebels at civilian targets in Saudi Arabia late last year.