Aden: Fighting raged on Thursday in Yemen’s battleground southern city Aden, a day after the United Nations declared its highest level humanitarian emergency in the war-torn country.

The new clashes left seven Al Houthi militiamen and five pro-government fighters dead, a military official said.

It comes after Al Houthi rocket fire on a residential district of Aden killed 31 civilians on Wednesday and left more than 100 others wounded, according to a medical official.

Al Houthi shelling on a western district of Aden early on Thursday damaged several homes and left casualties, residents said.

Meanwhile, a port near the Aden oil refinery came under Al Houthi artillery shelling for a fifth consecutive day and a blaze continued in the area, said Aden Refinery Company spokesman Nasser Al Shayef.

In the adjacent Lahj province and nearby Shabwa, Saudi-led coalition warplanes carried out several overnight strikes against Al Houthi positions, residents said.

The coalition has been bombing the Iran-backed Al Houthi militants since March 26 in support of Yemen’s President Abd Rabbo Mansour Hadi, who fled to Saudi Arabia.

The United Nations on Wednesday declared Yemen a level-three emergency, the highest on its scale, as aid chief Stephen O’Brien held talks to discuss the crisis in the impoverished Arabian Peninsula country.

More than 21.1 million people — over 80 per cent of Yemen’s population —are in need of aid, with 13 million facing food shortages.

A UN envoy expressed optimism late Wednesday that a humanitarian pause in the fighting in Yemen can still be reached in the two remaining weeks of Ramadan, to allow aid into war-ravaged country.

“We are still optimistic that we’ll obtain it,” Esmail Ould Shaikh Ahmad told AFP in the Saudi capital Riyadh, after a second day of talks with Yemen’s government in exile.

United Nations Secretary General Ban Ki-moon appealed for an immediate two-week humanitarian ceasefire before Ramadan began on June 18.

More than 80 per cent of the country’s population need aid and the health system faces “imminent collapse”, the UN says.

A five-day pause proposed by Saudi Arabia allowed some aid into Yemen in May before a Saudi-led coalition resumed air strikes, blaming ceasefire violations by Al Houthis.

UN peace talks in Geneva collapsed last month and Ould Shaikh Ahmad told AFP there is no “immediate plan” for a resumption.

“We prefer to go shuttling between the two parties until we can reach an agreement,” he said.

The envoy plans to visit the rebel-held Yemeni capital of Sana’a on Sunday for talks with Al Houthis and members of former president Ali Abdullah Saleh’s General People’s Congress party.

The aim, he told reporters, is “to reach a unified (agreement) hopefully before the end of Ramadan”.

He said there are “some guarantees” that any future truce will be respected more than the last one.

“What’s best is to have a comprehensive agreement, including monitors, to affirm that a truce is respected,” he said.