UNITED NATIONS, Dec. 3 -- With perhaps 250,000 Syrians cut off from aid in besieged communities across the war-torn country, greater efforts are needed to ensure real gains on the humanitarian front, a top UN official said on Tuesday.

Valerie Amos, the UN under-secretary-general for humanitarian affairs and emergency relief coordinator, made the remarks to reporters after her briefing at the UN Security Council on the current humanitarian situation in Syria.

"I advised the Security Council that we have seen some modest progress in terms of administrative procedures that had been put in place over time," she said, citing an increase in the number of relief distribution hubs and expedited visa processing.

However, there are an estimated 250,000 civilians trapped in besieged communities, while perhaps some 2.5 million are in hard- to-reach areas -- places that aid workers have been able to reach but not frequently enough to make any real headway against the overall needs, she added.

This is her second closed-door meeting with the 15-nation Security Council since the UN body adopted a Presidential Statement on Oct. 2, urging the Syrian government to immediately allow humanitarian access to relieve the plight of civilians trapped by heavy fighting, including cross-line aid deliveries.

The Presidential Statement, which urged all concerned parties to agree on humanitarian pauses in the fighting, especially in key delivery routes, deplored the escalating violence in a conflict that has killed more than 100,000 people and driven some 6.5 million others from their homes since the crisis erupted in March 2011.

On the implementation of the statement, Amos praised the government's decision to grant some 50 visas on an individual basis.

She also said that Damascus has given the UN humanitarian office permission to open three additional relief hubs. "But only two of these will actually be helpful to us, because the third being proposed -- Al Sweida -- will not allow us access into Western Dera'a, which is where the hard-to-reach communities are."

However, there were little progress on some of the more difficult areas -- protection of civilians, de-militarization of schools and hospitals, access to besieged communities and also cross-line access to hard-to-reach areas, she said.

"The issue is what is the best means to reach people in need. For me, the unity of the Security Council is the key here."

Meanwhile, UN agencies continue pressing ahead with relief efforts, with preparing civilians against the incoming winter season now a high priority.

Briefing the press in Geneva on Tuesday, Marixie Mercado, the UN Children's Fund (UNICEF) spokesperson, warned: "The scale of the humanitarian response needed for the looming winter is unprecedented, as the number quadrupled as compared to the previous year."

In December 2012, there were approximately 1.15 million children affected by the crisis inside Syria, with an additional 232,000 Syrian children living as refugees in neighboring countries, she said, adding that those numbers skyrocketed to 4.3 million and 1.2 million respectively this year.

UNICEF has been working since early October to equip children as quickly as possible for the cold. Blankets, plastic sheeting, winter clothing and hygiene kits are being distributed, along with winterized tents and fuel to heat classrooms.

For its part, the UN High Commissioner for Refugees (UNHCR) has commenced an emergency airlift of urgently needed winter supplies to reinforce its stockpile in northern Iraq where 50,000 Syrians refugees had poured in.

A UNHCR-chartered Boeing 777 landed at Erbil airport, the Kurdish region of Iraq, on Monday carrying 90 metric tons of relief items to help 4,400 families over the winter months, including plastic tarpaulins, thermal blankets, sleeping mats, jerry cans and kitchen sets.

"While UNHCR has adequate stocks inside Iraq to meet the immediate needs, we want to ensure that sufficient items are on- hand to address any developments," said UNHCR's Amin Awad from Amman. "The relief items we are airlifting will reinforce the UNHCR-led regional response as temperatures are starting to drop across higher altitude areas in the Syria region."

Elisabeth Byrs, spokesperson for the World Food Programme (WFP), told reporters that the agency dispatched enough food for more than 3.4 million people inside Syria in November and had reached eight more locations, which had been inaccessible in recent months.

However, she said the WFP remained gravely concerned about the fate of many Syrians still trapped in conflict zones throughout the country, including around Damascus and in Al Hassakeh, areas have been without food assistance for six consecutive months.

The WFP aims to reach 4 million people inside Syria every month and provide assistance for nearly 1.5 million refugees in neighboring countries.