GENEVA (AFP) - Some 420,000 people - half of them children - in the hard-hit Syrian region of Homs are in desperate need of humanitarian aid, the UN's children's agency said Friday.

"These people need life-saving assistance," UNICEF spokeswoman Marixie Mercado said, pointing out that many of the 420,000 people most in need of help were living in "shelters with blasted-in windows." "It's extremely cold, and you have 20 to 25 families in a room... These are harsh conditions for kids," she lamented, stressing that an acute lack of access to safe water and hygiene facilities coupled with children missing vaccinations was a recipe for disaster.

UNICEF staff took part in a UN joint mission to the devastated area last month, which determined that in addition to those most in need of aid, another 280,000 people were severely affected by the conflict.

Nearly one in three people in Homs, or some 635,000 people, had been displaced, Mercado said, adding that two-thirds of the displaced were under the age of 18.

Elisabeth Byrs of the UN's World Food Programme meanwhile said that 85 per cent of the people the agency helps across Syria have been displaced.

Mercado also lamented that the conflict was taking a heavy toll on children's access to education in the area, describing kids so eager to learn that they "fearlessly make their way through rubble" to makeshift schools.

Across Syria, one in four schools have been damaged, destroyed or are being used for shelter, according to UNICEF.

The UN's refugee agency also decried Friday the deteriorating situation in Syria.

"It is an appalling situation in Syria today," said Yacoub El Hillo, the head of UNHCR's Middle East and North Africa bureau, who also took part in the joint UN mission last month.

The country, where the UN estimates more than 60,000 people have been killed since the revolt against President Bashar al-Assad's regime began in March 2011, was "facing systematic destruction," he told reporters in Geneva.