A high-level UN delegation arrived in Yemen on Monday, a UN source said, to visit areas held by both the government and Huthi rebels across the crisis-hit country.
The executive directors of the World Health Organization, 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.
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 United Nations 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 ICRC on Monday warned that more than 600,000 Yemenis are expected to contract cholera by the end of the year.
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.