Yemen conflict: Houthis 'blocking Taiz aid deliveries'
The UN's aid chief has accused Yemen's Houthi rebel movement of obstructing the delivery of humanitarian assistance to the country's third city of Taiz.
Stephen O'Brien warned that up 200,000 vulnerable civilians were living under "virtual state of siege".
Houthi fighters were stopping aid lorries at checkpoints and allowing in only very limited assistance, he said.
Government forces, backed by a Saudi-led coalition, have been battling the rebels for control of Taiz for months.
At least 5,700 people have been killed, almost half of them civilians, since the conflict in Yemen escalated in March, when the coalition launched an air campaign after the Houthis forced President Abdrabbuh Mansour Hadi to flee the country.
Taiz, about 205km (123 miles) south of the rebel-held capital Sanaa, has suffered huge destruction since fighting in the city intensified in September.
Mr O'Brien, the UN's under-secretary for humanitarian affairs and emergency relief co-ordinator, said some 200,000 civilians trapped there were in dire need of drinking water, food, medical treatment, and other life-saving assistance and protection.
Civilian neighbourhoods, medical facilities and other premises around the city were continually hit by shelling, while checkpoints were preventing people from moving to safer areas and seeking assistance.
"Houthi and [allied] popular committees are blocking supply routes and continue to obstruct the delivery of urgently needed humanitarian aid and supplies into Taiz city," Mr O'Brien said.
"Despite repeated attempts by UN agencies and our humanitarian partners to negotiate access and reach people, our trucks have remained stuck at checkpoints and only very limited assistance has been allowed in," he added.
Mr O'Brien was alarmed by reports that some of the aid destined for Taiz had been diverted away from the people for whom it was intended, which he said was "unacceptable".
He also warned that those hospitals still functioning in Taiz were overwhelmed with wounded patients and faced severe shortages of doctors and nurses, essential medicines and fuel.