Fighting between pro-government forces and (STC) in Yemen''s second city Aden has killed around 40 people and injured 260 others including civilians, the UN said Sunday.

"Scores of civilians have been killed and wounded since August 8 when fighting broke out in the city of Aden. Preliminary reports indicate that as many as 40 people have been killed and 260 injured," a UN statement said.

"It is heart-breaking that during Eid al-Adha, families are mourning the death of their loved ones instead of celebrating together in peace and harmony," UN Humanitarian Coordinator in Yemen Lise Grande said.

"Our main concern right now is to dispatch medical teams to rescue the injured," she said.

"We are also very worried by reports that civilians trapped in their homes are running out of food and water," Grande added, urging the belligerents to protect civilians.

"Families need to be able to move freely and safely to secure the things they need to survive.

"We are asking authorities to guarantee unimpeded access for humanitarian organisations," she said.

The clashes flared on Wednesday between fighters of the Yemeni government and combatants from the so-called Security Belt who are dominated by separatists seeking an independent south.

The southern port city of Aden has been the base of the Hadi government since it was driven from the capital Sanaa by the rebels more than four years ago.

The coalition has called for a ceasefire and an "urgent meeting" between the warring parties.

Both the Yemeni government and (STC) said early Sunday they backed Riyadh''s call for dialogue and a suspension of fighting.

But in a sermon to mark the start of the Muslim Eid al-Adha festival, Southern Transitional Council (STC) vice president Hani bin Breik said his group will not "negotiate under threat".