More than 140 rebels and pro-government troops have been killed this week as fighting intensifies for Yemen's strategic northern city of Marib, military and medical sources told AFP Friday.
At least 51 loyalists were killed in the past four days, most of them in clashes in the province of Shabwa and the neighbouring governorate of Marib, multiple military sources said.
They added that at least 93 Iran-backed Huthi rebels also died in the fighting and from air strikes by the Saudi-led military coalition backing the government.
The Huthis rarely report casualty numbers, but figures were confirmed by medical sources.
The Huthis in February escalated their efforts to seize Marib, the government's last northern stronghold, and the fighting has killed hundreds on both sides.
Control of the oil-rich region would strengthen the Huthis' bargaining position in peace talks.
According to the military sources, who spoke on condition of anonymity, the Huthis have made advances and seized four districts -- one in Marib and three in Shabwa.
"Three districts in Shabwa have fallen in limited clashes and within hours," one official told AFP.
- Humanitarian crisis -
Yemen's conflict flared in 2014 when the Huthis seized the capital Sanaa, prompting Saudi-led intervention to prop up the internationally recognised government the following year.
This month marks seven years since the rebels took control of Sanaa, with some analysts saying the balance has tilted in favour of the insurgents against the coalition.
Earlier this week, Swedish diplomat Hans Grundberg, the United Nations's new envoy for Yemen, was in Oman, which has played a mediating role in the Yemen conflict.
He met with Omani and Huthi officials, including top rebel negotiator Mohammed Abdulsalam.
"Sustainable peace can only be achieved through a peacefully negotiated settlement," said Grundberg, according to a statement on Tuesday.
"It is imperative that all efforts are directed towards revitalising a political process that can produce lasting solutions that meet the aspirations of Yemeni women and men."
While the UN and Washington are pushing for an end to the war, the Huthis have demanded the re-opening of Sanaa airport, closed under a Saudi blockade since 2016, before any ceasefire or negotiations.
The last talks took place in Sweden in 2018, when the opposing sides agreed to a mass prisoner swap and to spare the city of Hodeida, where the port serves as the country's lifeline.
But despite agreeing to a ceasefire in Hodeida, violent clashes have since broken out between the rebels and pro-government troops around the strategic city.
Fighting across the country has killed tens of thousands and left about 80 percent of Yemenis dependent on aid, in what the UN calls the world's worst humanitarian crisis.