Yemen's government forces are battling al-Qaeda fighters in the country's south, aiming to push back advances the group has made during a year-long civil war for which peace talks are currently under way in Kuwait.
Dozens of fighters loyal to Al-Qaeda in the Arabian Peninsula (AQAP) were killed in the clashes, residents and a military source said on Saturday, while a drone strike killed two others further north.
Fighting across Yemen has killed more than 6,800 people and driven more than 2.5 million from their homes since March last year, according to the United Nations.
Ismail Ould Cheikh Ahmed, the UN envoy for Yemen, described as "constructive" the first full day of peace talks while calling for a halt to air strikes by an Arab coalition and missile fire by Houthi rebels.
He said reinforcing an April 11 ceasefire was essential to the success of the negotiations in Kuwait.
Ould Cheikh Ahmed, who spent months getting the rival sides to the negotiating table, said Friday's talks had been "very constructive".
"There was a consensus on strengthening the ceasefire and the two sides were committed to the need to achieve peace and that this is the last opportunity," he said.
AQAP has taken advantage of chaos in Yemen since last year to win control over swaths of southern and eastern Yemen, creating a local government there and introducing services.
The Houthis have held Yemen's capital, Sanaa, since September 2014 and their advance prompted an Arab coalition air campaign in support of President Abd-Rabbu Mansour Hadi's government.
Despite Ould Cheikh Ahmed's positive comments, a government source said disputes continued in the talks over both the agenda and accusations from the government that the Houthis and former president Ali Abdullah Saleh's forces had breached the truce in the city of Taiz.
The government wants the Houthis and Saleh's forces to withdraw from cities and hand over weapons before discussing a solution to the political disagreements.
The Houthis and its allies want a unity government to be formed before disarmament talks.
Al Jazeera's Hashem Ahelbarra, reporting from the talks in Kuwait City, said a major hurdle in the negotiations was a "huge trust deficit" between the warring sides.
READ MORE: Yemen revolution - 'Our dream was sold'
"The UN envoy along with the different factions are trying to work on confidence-building measures and start a political process with the aim of forming a national unity government," he said.
"For the UN this is a very critical moment. They have to seize the opportunity or there is not going to be peace any time soon."
Ould Cheikh Ahmed, the UN envoy, said the rebels complained of continuing air strikes by the Arab coalition while the government side complained of continued ceasefire violations by the rebels.
The envoy said he had contacted Saudi Arabia about the coalition air strikes and they had said the raids were ordered only in response to ceasefire violations by the rebels.
"The ceasefire is respected between 70 percent to 80 percent all over Yemen," he said.
The war has taken on regional implications, as Sunni-ruled Saudi Arabia accuses regional Shia rival Iran of arming and training the Houthis.
Iran says it only provides the rebels with political support, though the US navy says its sailors and allies have seized weapons heading for Yemen from Iran.
Source: Al Jazeera and agencies