Yemen's government has accused Houthi rebels of using civilians as human shields in their renewed offensive against a strategically important mountainous region in the north.
Earlier this month, the Iran-backed rebels resumed their efforts to capture the city of Marib, 120 kilometres east of the rebel-held capital, Sanaa.
Military officials on Saturday said the rebels had been using residents of Al Zor camp in Marib province's Sirwah district as human shields, since their capture of that area last week.
Marib lies close to some of Yemen's richest oil fields and its capture would be major prize for the Houthis.
Local tribes, backed by the government and Saudi airpower, have resisted fiercely, using their knowledge of the mountainous terrain to their advantage.
But the fighting has raised fears for the hundreds of thousands of displaced civilians sheltering in camps in the surrounding desert that extends to the Saudi border.
The officials said there had been no let-up in the fighting.
Over the past 24 hours, at least 12 government-aligned fighters and 20 Houthis had been killed in clashes north and west of Marib, they said.
There was no way to independently verify the death toll.
Until early last year, Marib had been spared the worst of the civil war that erupted in 2014.
The International Committee of the Red Cross (ICRC) said it is "extremely concerned" by the recent fighting.
"The ICRC urges all parties to the conflict to take every possible measure to protect the civilians, their properties and all civilian essential infrastructures," it said.
The UN has warned of the potential for a humanitarian disaster.
"It puts millions of civilians at risk, especially with the fighting reaching camps for internally displaced persons," envoy Martin Griffiths told the UN Security Council.
The US on Thursday urged the Houthis to end their offensive and to allow as much access for humanitarian relief as possible.
On Friday the UK government called for an end to the fighting.
The Houthi offensive came as the new US administration removed the rebels from Washington's blacklist of terrorist organisations in a bid to facilitate aid deliveries to rebel-held areas and pave the way for renewed peace talks.
President Joe Biden has also announced an end to US backing for Saudi operations in Yemen.
Observers say the Houthis want to capture Marib to strengthen their hand in eventual peace negotiations.