ADEN: UN aid chief Stephen O'Brien was "denied passage" to Yemen's third largest city Taez, a UN statement said.
"O'Brien's convoy was denied passage at the final checkpoint before crossing the frontline" into Taez, said a statement by the UN's Office for the Coordination of Humanitarian Affairs (OCHA).
He was denied access to the flashpoint city "despite having received assurance of safe passage by all parties", the statement said.
OCHA did not name the party that prevented O'Brien's convoy from proceeding, but the route from the north to Taez is controlled by the rebels and their allies.
"After being denied access, the convoy returned to safer ground to continue negotiating access with the authorities controlling the final checkpoint, but to no avail," OCHA said.
"O'Brien was extremely disappointed that humanitarian efforts to reach people in need were once again thwarted by parties to a conflict, especially at a time when millions of Yemenis are severely food insecure and face the risk of famine," it added.
A local official told AFP earlier that O'Brien was stopped at a rebel checkpoint in Hizran, 15 kilometres (nine miles) northwest of Taez, while the government-run news agency Saba accused Huthi rebel forces of opening fire at his convoy.
In a statement carried by Saba, the government said the rebels blocked O'Brien's access to Taez to "prevent the truth about the situation in the city, including a suffocating siege... from reaching the world".
