Ismail Ould Cheikh Ahmed, the UN special envoy to Yemen, has arrived in the country's capital in a bid to arrange a pause in fighting until the end of the Muslim holy month of Ramadan on July 17, to allow for deliveries of humanitarian aid.
The visit by Ould Cheikh Ahmed, who arrived on Sunday for talks with the Houthis and their allies, comes amid continuing violence, including a deadly attack on a market in northern Yemen, according to a Houthi news agency.
Houthi spokesman Mohammed Abdul Salam said in a post on his Facebook page that he had met Ould Cheikh Ahmed on Friday in Muscat, Oman's capital, in a meeting attended by the ambassadors of the European Union and Germany.
Political sources in Muscat said Arab forces had demanded guarantees that the Houthis and allied army units would not use any pause during Ramadan to keep advancing on areas held by forces allied or loyal to exiled President Abd-Rabbu Mansour Hadi in south and eastern Yemen.
On Friday, the UN alerted aid groups to be prepared for a possible humanitarian pause in the fighting that would allow them to deliver help to some of the 21 million people in need.
Air strikes by Arab coalition forces have killed dozens of civilians in an attack on a market in northern Yemen, according to the Houthi-run news agency Saba.
Saba said Sunday's air strike targeted the Aahem market in Hajjah province, where preliminary figures showed that 30 civilians were killed and an unspecified number of people were wounded.
The news agency also said Houthi forces launched rockets against a number of Saudi army positions, including a military airport in the southern city of Najran, in response to what it described as Saudi aggression against Yemen.
An Arab coalition, including Saudi Arabia, has been targeting Houthi rebel forces and allied army units loyal to former President Ali Abdullah Saleh since March in a campaign to restore Hadi to power.
"The Saudi enemy targeted citizens while they were doing their shopping at Aahem market," the agency quoted a security source in Hajjah as saying.
Residents confirmed an air strike on the market but gave no figures on casualties, saying the Houthis closed off the area and were transporting casualties to local hospitals.
On the attacks on Saudi military positions, Saba said that Yemeni forces allied with the Houthis launched several strikes on al-Sharafa army camp and the military airport in Najran and on tanks stationed in the Saudi province of Jizan.
It said one Saudi soldier was killed at an observation tower in Dhahran Aseer, where an armoured vehicle was also destroyed, while a tank was destroyed and dozens of soldiers were wounded at al-Makhrooq post in Najran when it was attacked with artillery and rocket fire.
The UN last week designated the war in Yemen as a Level 3 humanitarian crisis, its most severe category.