Some 10,000 families have fled the northern Yemeni city of Amran in three days to escape an intensified battle between the army and Shiite rebels, the Red Crescent said Tuesday.
Launching a "call for help," the organisation said 5,000 more families were trapped by fighting inside the city.
Amran, 50 kilometres (30 miles) north of Sanaa, is home to an estimated 120,000 inhabitants.
It has been the scene of fighting between troops and Huthi rebels -- also known as Ansarullah -- as well as tribes on both sides since February as the rebels advanced from their mountain strongholds towards the capital.
"The bodies of 60 people killed, mostly civilians and soldiers, have been brought to the hospital since Saturday," said a medic at Amran's main hospital.
"Around 180 wounded, many of them civilians, were also admitted," the source told AFP, which could not immediately compile a full toll.
Army reinforcements sent to Amran Sunday were locked in fierce clashes with rebels in Dharawan, 15 kilometres from Sanaa, and in and around the city itself, military sources said.
Early on Tuesday, fighter jets bombed Amran's Warak neighbourhood, hours after it was seized by rebels.
Huthis have been battling the government for years from their Saada heartland, complaining of marginalisation under former president Ali Abdullah Saleh, who stepped down in 2012 after a year-long uprising.
Clashes erupted anew last month in the north, ending an 11-day truce agreed after mediation backed by UN envoy Jamal Benomar.
In a statement published on the official Saba news agency Tuesday, Benomar said he "is deeply concerned about the continuing violence in Amran and other areas of the north."
"He profoundly regrets the heavy loss of life over the past days," said the statement.
He "stresses the need for all parties to work toward a definitive cessation of violence through a political process" and "reiterates the need to develop a peace plan for the north," it added.
Benomar also urged "all sides to facilitate safe and unhindered humanitarian access to evacuate the wounded and to ensure the delivery of assistance to all populations in need."
The rebels say a federalisation plan agreed in February after national talks as part of a political transition would divide Yemen into rich and poor regions.
They seized areas of Amran province in fighting with tribes in February that killed more than 150 people.