A UN envoy called for an extension of a humanitarian ceasefire in Yemen due to expire on Sunday as the Houthi Shiite rebels boycotted political talks in Riyadh.
The appeal followed clashes on the ground between rebels and pro-government forces that killed dozens across south Yemen on Saturday despite the truce, which has largely held.
"I call on all parties to renew their commitment to this truce for five more days at least," UN envoy to Yemen Ismail Ould Sheikh Ahmed said in the Saudi capital.
"This humanitarian truce should turn into a permanent ceasefire," the Mauritanian diplomat added.
Aid groups have also called for a lasting truce in the impoverished country, where a Saudi-led regional coalition has been waging an air war on the Iran-backed Houthis since late March.
Yemeni political parties began talks Sunday in the Saudi capital aimed at finding a political solution to the crisis.
But the Houthis stayed away from the meeting of about 400 delegates including President Abd Rabbu Mansour Hadi, who has taken refuge in Riyadh.
The war has sent tensions soaring between Sunni-ruled Saudi Arabia and its Shiite rival Iran, which has vehemently denied accusations it armed the Houthis.
An Iranian aid ship bound for Yemen in defiance of US warnings has entered the Gulf of Aden and is expected to reach port on Thursday, media in Tehran reported.
The ship's mission has been overshadowed by US calls for it to head to a UN emergency relief hub in Djibouti instead of docking in the Yemeni port of Hodeida.
Clashes raged overnight Saturday in the central city of Taez between rebels -- supported by troops loyal to ousted president Ali Abdullah Saleh -- and pro-Hadi forces.
The rebels, who seized the capital in September and have since swept across many other regions, bombed a village south of Taez city, killing 14 civilians, a local official said.
Sporadic clashes also continued in Aden, which has been the scene of fierce fighting since rebels advanced on the southern port city in late March after Hadi took refuge there.
The United Nations has expressed deep concern about the civilian death toll from the Saudi-led bombing as well as the humanitarian impact of an air and sea blockade imposed by the coalition.
It says more than 1,500 people have died in the conflict since late March.
Some aid has trickled into Yemen since the pause in fighting, but residents of areas where clashes persist complain they remain without the most basic supplies.
The United Nations has called for the Saudi-led coalition to simplify import inspections after warning that supplies were still blocked.
A UAE ship carrying 1,200 tonnes of food supply docked in Aden on Saturday, according to Naef al-Bakri, undersecretary of the Aden governorate.
Saudi Foreign Minister Adel al-Jubeir has accused the Houthis of repeatedly violating ceasefire terms.
The Houthis are boycotting the three-day meeting in Riyadh, insisting on holding the talks in Yemen.
But representatives of Saleh's General People's Congress party will be present.
Among the goals of the meeting is working towards a constitution which would be presented to the Yemeni people, "and to hold a referendum to put the results of the dialogue into practice," according to Abdulaziz al-Jaber, head of the conference's organising committee.
Saudi Arabia previously hosted Gulf-sponsored meetings that sealed a deal to ease Saleh out of office in February 2012 after a year of deadly nationwide protests against his three-decade rule.
The chaos in Yemen has been exploited by armed groups, including the country's branch of Al-Qaeda, which is viewed by the United States as the world's most dangerous branch of the network.
Three suspected militants were killed late Saturday in a US drone strike that targeted a vehicle transporting weapons in Habban, in southern Shabwa province, a tribal chief said.
The extremist group has controlled Mukalla, the capital of Yemen's vast desert Hadramawt province, since April and has for months claimed deadly attacks against Yemen's government-controlled armed forces.
A local official said 36 Yemen soldiers were kidnapped on Friday by suspected Al-Qaeda members in Mukalla.