The top United Nations aid official landed in the Yemeni port city of Aden Tuesday, embarking on a five-day trip aimed at drawing attention to the cholera-stricken country.

"I decided to come to Yemen because I am deeply concerned about the humanitarian crisis that has continued to deteriorate," said Emergency Relief Coordinator Mark Lowcock.

It is his first visit to Yemen since assuming the post on September 1.

Lowcock said the trip would include meetings with officials in Aden, the seat of the internationally recognised government, as well as regular Yemenis impacted by the conflict.

"I plan to meet many of the most vulnerable Yemeni people we serve to listen to their concerns and aspirations, and take their stories to the international community," he said.

Humanitarian responders have this year provided direct aid to more than seven million Yemenis living on the brink of famine, according to the UN Office for the Coordination of Humanitarian Affairs.

Since 2014, a rebel alliance has fought Yemen's UN-recognised government of President Abedrabbo Mansour Hadi for control of the impoverished country.

A Saudi-led coalition supporting the Hadi government imposed an air and sea blockade on all rebel-held territory in March 2015 saying it was the only way to stop weapons smuggling.

The UN has listed Yemen as the world's number one humanitarian crisis.

More than 8,650 people have been killed in the conflict and around 58,600 others have been wounded, many of them civilians.