Young Syrian refugees from Aleppo beg with their mother (L) on the steps of a bank in a street in Beirut on September 18, 2013.

Also in urgent need of action are Lebanese and Palestinian children who live in poor, marginalised areas of Lebanon, where public health and education services have become massively overstretched by the refugee crisis.

UNICEF's statement comes after a visit to the small Mediterranean country by director Anthony Lake, who met with President Michel Sleiman and caretaker Prime Minister Najib Mikati.

"Particular concerns were shared about the impact of the approaching winter months, and the need for urgent action to prepare for this especially challenging period," said UNICEF.

Ever since the outbreak of Syria's war in 2011, which has killed more than 120,000 people and forced millions to flee their homes, Lebanon has become host to the highest proportion of refugees.

According to UN figures, of the 805,000 Syrian refugees in Lebanon, half are children.

Lake praised Lebanon for its efforts to cope, but said global action is needed to ensure vulnerable children can get through the winter.

"The international community has not only a humanitarian obligation to the children but a responsibility to match Lebanon's commitment," Lake said.

Long marred by political and economic difficulties of its own, Lebanon has been struggling to deal with the influx of refugees from neighbouring Syria.

Unlike Turkey or Jordan, where the refugee population is smaller, Lebanon has not allowed official refugee camps to be set up.

Instead, fleeing Syrians have had to seek refuge in the host communities.

Some can afford housing in apartments in the cities, but many have no choice but to live in tents in the countryside.

Many others are sleeping on the streets, and child labour is on the rise.

According to Luciano Calestini, UNICEF's deputy director in Lebanon, "more than 100,000 Syrian children are living in informal tent settlements.

"The winter as we've seen in the last few years presents a very critical risk, especially for those living in such settlements."

UNICEF wants to ensure children have adequate footwear and clothing, and also that schools have fuel for heating.

In order to be able to cope, the public health system must also be strengthened, Calestini said, adding that marginalised Palestinian and Lebanese children will also suffer if the public sector is not strengthened.

"We all well know that the majority of Syrians have settled in the poorest parts of the country. The biggest burden on Lebanese public services is in those locations," Calestini told AFP.

UNICEF Lebanon had appealed for $125 million (92.6 million euros) to fund its response to the Syrian refugee crisis. It has received $100 million.

"We're now at the end of the year. Donors have been extremely generous. But the troubling news is the crisis keeps growing. There is no diplomatic solution in sight.

"For 2014, we call on the donor community to continue to support us at the same level," said Calestini.