Pro-government fighters in south Yemen seized control on Tuesday of Aden's airport after fierce battles with Houthi fighters, military sources have said.

Aided by warplanes from the Saudi-led coalition, gunmen from the Popular Resistance militia also pushed back the Shia Houthi fighters and their allies from areas within the war-torn port city, the sources said.

Warships off the coast of Aden took part in the battle which a presidential official said was part of a new military campaign to regain control of all the city.

Exiled President Abd Rabbuh Mansour Hadi is "personally supervising the operation" dubbed "Operation Golden Arrow for the Liberation of Aden," said his office director Mohammed Marem from Aden.

Soldiers of the 39th Armoured Brigade had captured Aden's airport on 25 March after switching allegiance to the Houthi militia.

The Houthis and allied troops have since gone on to seize the presidential palace and other parts of Aden, the second-largest city in Yemen and its main sea port.

Military sources in Aden have said that pro-Hadi fighters were now being backed up with ground support from Yemeni forces recently trained in Saudi Arabia, AFP reported.

Significant gain

It comes a day after airstrikes bombed Houthi positions in capital Sanaa, while clashes occurred between Houthi forces and pro-government fighters in the southern city of Taiz, despite a UN-declared truce aimed at delivering desperately needed aid.

The truce, which was supposed to come into effect on Friday, was broken within hours, with accusations of breaches on both sides.

UN chief Ban Ki-moon said he was "very much disappointed" by Yemen's failed ceasefire but retained hope that the fighting might still end, his spokesman said.

US-Saudi talks

US President Barack Obama and Saudi Arabia's King Salman on Tuesday discussed the "urgent" need to end fighting in Yemen, hours after Saudi-backed loyalists retook control of Aden airport.

The White House has repeatedly pressed for an end to the conflict in which Saudi Arabia has led a coalition air and naval campaign south of its border.

It has also called for talks to end the crisis.

Leading Sunni power Saudi Arabia has been deeply concerned about Iranian influence in its impoverished southern neighbor.

Riyadh launched a devastating air campaign in March against the rebels and their allies in the armed forces.

Humanitarian disaster

The United Nations has declared Yemen a level-3 humanitarian emergency, the highest on its scale.

More than 21.1 million people - over 80 percent of Yemen's population - need aid, with 13 million facing food shortages, while access to water has become difficult for 9.4 million people.

The UN says the conflict has killed more than 3,200 people, about half of them civilians, since late March.

Despite the fighting, refugees from the Horn of Africa continue to arrive in Yemen, the UN High Commissioner for Refugees said in Geneva.

Johannes Van Der Klaauw, the UN's humanitarian coordinator for Yemen, said 37,000 migrants arrived this year - almost one-third of them after the coalition began its air strikes.