A high-level United Nations delegation arrived in Yemen on Monday to visit areas held both by the government and the Houthi rebels across the crisis-hit country, according to a UN source.

The executive directors of the World Health Organisation (WHO), the UN Children's Fund (UNICEF) and the World Food Programme visited the southern province of Aden, where the government is based, and the rebel-held capital Sanaa, the source said on condition of anonymity.

UNICEF and WHO representatives declined to elaborate on the visit to the Arabian Peninsula country, where war, cholera and looming famine have killed thousands of people and displaced millions.

READ MORE: Yemen crisis 'an absolute shame on humanity'

The three UN officials met Prime Minister Ahmed bin Dagher for talks on international aid, state news agency Saba reported.

WHO director Tedros Adhanom Ghebreyesus said the visit aimed to contain "the cholera epidemic which has spread to all provinces", Saba said.

On Sunday, the UN warned that two thirds of Yemen's population of 27 million needed humanitarian assistance, with 10 million civilians in acute need of life-saving aid as the country teeters on the edge of famine.

A cholera outbreak has independently claimed 1,800 lives and infected more than 370,000 others, according to both the WHO and the International Committee of the Red Cross (ICRC).

'The world is sleep-walking'

The ICRC on Monday warned that more than 600,000 Yemenis are expected to contract cholera by the end of the year.

Peter Maurer, the head of ICRC, also made a rare visit to the front lines in the besieged western city of Taiz on Monday to take a first-hand look at the country's humanitarian crisis

"I find this needless suffering absolutely infuriating," Maurer said on Sunday. "The world is sleep-walking into yet more tragedy."

Maurer told Al Jazeera that ICRC doubled its aid program for Yemen a couple of weeks ago.

"What we are doing at the present moment is to increase our preventive efforts in waste collection, water cleaning systems and water repair systems, which is important to prevent the further spread of cholera," he said, from Taiz.

War between the Saudi-backed government and Iran-backed rebels in one of the world's most impoverished countries has killed more than 8,000 people and wounded a further 44,500 since Riyadh and its allies joined the conflict in 2015.

A string of vital ports along Yemen's Red Sea coast are blockaded, leaving millions of people with limited access to food and medicine.

Less than half of the country's medical facilities are currently functional.

Seven UN-brokered truces have failed to end the conflict.