UN Secretary-General Antonio Guterres expressed concern over reports of a second drone attack on Wednesday on a Saudi airport, for which the Houthis have claimed responsibility.
The UN spokesman Stephane Dujarric said: "He condemns these attacks, as well as any attack targeting civilians and civilian infrastructure, which violate international humanitarian law,".
The UN chief "also calls on all the parties to the Yemen conflict to exercise maximum restraint and prevent further escalation amid heightened tensions."
"The secretary-general reminds the parties that a more productive path forward exists -- and that is through dialogue." Dujarric said.
Guterres calls on all parties to work constructively with his special envoy for Yemen, Martin Griffiths, to make more progress in the implementation of the Stockholm Agreement as well as efforts to end the conflict.
The Houthi group in Yemen said Wednesday it launched an attack on the Saudi Najran airport with unmanned aerial vehicle (UAV), the second within 24 hours.
The Houthi drone air force attacked the warplane park at Najran airport using k2 Qasif drone, the Houthi-run Al-Masirah TV reported.
No immediate comment has be issued by the Saudi-led coalition on the Houthi claim, and no casualties or damages have reported.
Yemen has been racked by a 4-year bloody conflictbetween the internationally-recognized Yemeni government's forces, backed by a Saudi-led coalition, and the Iranian-backed Houthi rebels who ousted the government in 2014.
Houthis sporadically fire ballistic missiles on Saudi territory "in reply to coalition airstrikes that target Yemeni civilians and infrastructure," while Saudi Arabia accuses Iran of providing Houthis with such missiles.
On Tuesday, the group claimed its drones hit an arms depot in Najran airport, enflaming the place, after the coalition had said the rebels tried to target civil establishment in Najran city with bomb-laden UAV.
On the 6th of this May, Saudi authorities announced resumption of flights at Najran airport, after 4-year stop "for security fears about passengers and planes safety lest come under Houthi fire."
On Sunday, Houthis said they have a "bank of 300 vital targets in Saudi Arabia and United Arab Emirates" leading the coalition in support of the internationally-recognized government of President Hadi.
Saudi media have reported the Kingdom's air defense intercepted early on Monday two ballistic missiles over Taif and Jeddah cities, claiming they were fired by Houthis, who have denied.
The first missile was intercepted over Taif City, while heading for Mecca, and the other over the Red Sea city of Jeddah, Al-Arabiya quoted eyewitnesses as saying.
Lastweek, two Saudi oil pumping stations were attacked in Riyadh region, and the Iranian-backed rebels claimed responsibility, saying they used 7 drones in the attack.