Fighting between Yemeni government forces and rebels has trapped tens of thousands of civilians in and around the port town of Mokha, where over 30 fighters were killed Wednesday, residents and the UN said.
"We fear the (Shia) Houthi (rebel) snipers who have taken up positions on rooftops but also the firing from the other (government) side," said Majed Mukaibar, a 32-year-old fisherman and father in the Red Sea town of southwest Yemen.
Ibrahim Saleh, a tradesman who works in southern Yemen's main city of Aden, told AFP that he has been trying since last week to evacuate his family from Mokha but has been thwarted by incessant gunfire.
The UN humanitarian coordinator in Yemen, Jamie McGoldrick, said in a statement released Tuesday that he was "extremely concerned about the safety and well-being of civilians" in Mokha and nearby Dhubab.
"Information from the field indicates that military operations in the coastal region have forced most residents of Dhubab to flee the area," he said.
McGoldrick said "an estimated 20,000-30,000 people, almost one third of the population, are trapped in the town (of Mokha) and require immediate protection and relief assistance".
Constant air strikes, shelling and sniper fire around the town had "killed and injured scores of civilians and have ground most services to a halt", including water supplies.
The UN official appealed for a halt to fighting "to facilitate the delivery of assistance to Mokha and enable the free movement of civilians".
Military and medical sources said 25 rebels and six soldiers on the government side, which is being supported by a Saudi-led Arab coalition, were killed in the latest clashes on Wednesday for control of Mokha.
Forces loyal to President Abedrabbo Mansour Hadi have been battling on three fronts but so far failed to penetrate the centre of Mokha, according to residents and military sources.
Before government forces launched a major offensive on January 7, Houthi rebels controlled virtually all of Yemen's 450-kilometre (280-mile) Red Sea coastline.
Soldiers have since thrust north from the Bab al-Mandab strait where the Red Sea joins the Indian Ocean, overrunning Dhubab district and entering the historic port of Mokha in their biggest advance in months.
Conflict in Yemen escalated in March 2015 when the Saudi-led coalition launched air raids against the Houthi rebels, who had taken over the capital and seized swathes of the country's centre and north.
The war has cost more than 7,400 lives in the past two years, according to the UN's World Health Organisation.