Yemen's Iran-backed Houthi rebels are continuing their advance on the government's last northern stronghold despite heavy casualties, military sources said on Sunday.
But the government denied earlier reports that the rebels had taken control of an area in the north-west in their march on Marib city, which has been condemned by the UN and the broader international community.
Yemeni Information Minister, Muammar Al Eryani, on Sunday disputed reports that the Houthis had taken Kassara and were making progress on the western fronts.
"We confirm that National Army and Popular Resistance in Marib are steadfast in their positions on various fronts," Mr Al Eryani wrote on Twitter.
Marib and its surrounding oilfields are the last significant pocket of government-held territory in the north, the rest of which is under rebel control, including the capital Sanaa.
Fierce fighting has left at least 65 dead over the past two days, including about 26 loyalist personnel, among them four officers, the government sources told AFP.
Military officials claimed fighting had moved to Al Mil, six kilometres from the centre of Marib.
But the mountains around Al Mil remain a formidable barrier to the rebels, who have been battling to reach Marib since February.
Government sources said the Houthis had poured in hundreds of reinforcements in recent days.
Observers say the Houthis are intent on capturing the city for leverage before any negotiations with the government, amid a US push to revive peace talks.
The city's fall could also lead to a humanitarian disaster, as vast numbers of civilians displaced from fighting elsewhere have sought refuge in the area.
About 140 camps have sprung up in the surrounding desert to provide basic shelter for up to two million displaced, the Yemeni government said.
Hundreds of combatants have been killed since the large-scale offensive began, with the toll fuelled by wave after wave of Houthi fighters arriving on frontlines around the city.
A government commander told AFP in Marib this month that the Houthis are sending in young recruits, many of them children.
The escalation in hostilities has displaced 13,600 people in Marib this year, according to the UN refugee agency, putting a heavy strain on the city in the middle of a second coronavirus wave.
Makeshift settlements, lacking clean water and electricity, are overflowing and camp residents say they have repeatedly come under Houthi shelling.
The rebels have also increased missile and drone strikes against neighbouring Saudi Arabia in recent months, demanding the opening of Yemen's airspace and ports.
They have rejected a Saudi proposal for a ceasefire.
The administration of US President Joe Biden is mounting a renewed push to end the conflict, warning that the suffering will only end with a political solution.