UN Special Envoy to Yemen Hans Grundberg visited Iran to discuss expanding a fragile truce in Yemen after weeks of escalation by the Iran-backed Houthi militia, his office said on Monday.
Mr Grundberg held talks with Iran's Foreign Minister Hossein Amir Abdollahian and other officials.
"Discussions focused on efforts to extend and expand the truce in Yemen as well as current regional dynamics," his office said on Twitter.
Mr Grundberg's trip to Iran, his first since he was appointed in August last year, comes as he seeks a third extension to the UN-brokered truce that began in April.
However, his efforts might be complicated by a recent increase in military activity by the Houthi rebels against government forces.
Last week, the Iran-backed group killed 10 members of Yemen's army and wounded seven others in an attack in Taez. Yemen's armed forces said they had been staving off tens of Houthi attacks on the besieged city in the south-west.
Under the truce, which Mr Grundberg has called "fragile", the Houthis were supposed to reopen the roads around Taez to allow aid residents to travel and to allow aid to enter.
Pro-government Yemeni activists and politicians have been growing increasingly wary of a further extension of the truce, which expires this month.
Mr Grundberg's visit to Iran is not the first by a UN envoy to Yemen.
His predecessor, Martin Griffiths, made a similar trip last year where he met then foreign minister Javad Zarif in a bid to reach a political solution to the conflict.
Mr Grundberg's efforts have, for the first time in the seven years, brought a few months of peace across the country with a significant reduction in violence across front lines.
Yemen has been in a state of conflict since the Houthi takeover of the capital Sanaa in 2014 and the subsequent intervention by a Saudi-led coalition on behalf of the government to restore it to power.
