The head of the Swiss-run International Committee of the Red Cross (ICRC) says he hopes Monday's ceasefire will allow more aid to reach civilians in Lebanon.
Jakob Kellenberger was speaking just hours after a United Nations truce to end the fighting in Lebanon between Israel and Hezbollah came into force.
"My strong hope is that developments since this [Monday] morning will make it easier for us to reach all the civilians in need of assistance," Kellenberger said in a statement released after a media conference in Geneva on Monday.
He added that two major relief shipments had already got through to the southern Lebanese Tyre region and to the village of Hula.
Thousands of displaced Lebanese have begun flooding into the south of the country after the ceasefire took effect early on Monday morning, prompting fears by relief agencies about a worsening of the humanitarian situation.
Kellenberger said that the 400,000-500,000 people who had stayed in the area still needed immediate aid. Evacuating the injured and finding bodies, as well as providing water, fuel and medication remained the most pressing challenges, he added.
"We must gain access as quickly as possible to certain villages in the south of Lebanon where there has been fighting," Kellenberger told reporters.
He added that it was difficult to know at what pace displaced people would return to the region, but said that they would receive aid as well.
The ICRC president has just returned from a four-day visit to southern Lebanon and Israel in which he said he received pledges from Israeli Prime Minister Ehud Olmert to gain better access for the ICRC in southern Lebanon.
Kellenberger had insisted that improved access was essential given the desperate humanitarian situation.
However, he said on Monday that the ICRC had not yet been allowed to see the three Israeli soldiers kidnapped by Hezbollah and Hamas, which operates from the occupied territories. He said that the ICRC would continue to pursue this demand with energy.
But he said that since Sunday the Israeli authorities had given the ICRC permission to organise family visits for Palestinian detainees.
The UN Security Council resolution seeking a "full cessation" of violence between Israel and Hezbollah has been welcomed by members of the international community, including Switzerland. Bern has said it will continue supporting peacekeeping efforts financially.
The resolution, adopted unanimously, authorises 15,000 UN peacekeepers to help Lebanese troops take control of south Lebanon.
On Monday UN Secretary General Kofi Annan said the ceasefire seemed to be holding.
Israel has said that it would continue to maintain an air and sea blockade of Lebanon and that its troops would return fire if they came under attack.
Olmert has also warned that Israel will pursue Hezbollah leaders in Lebanon despite the ceasefire.
For his part, Hezbollah leader Sayyed Hassan Nasrallah said on Monday that his group had achieved a "strategic, historic victory" against Israel.
swissinfo with agencies
The UN-backed ceasefire came into effect at 0500 GMT, although there was one later clash in which Israeli soldiers fired onto a group they said were militants.
Thousands of displaced people have flooded back into southern Lebanon and aid workers, including the ICRC, have been rushing to send supplies into the region.
The ICRC said on Monday it aims to assist at least 200,000 internally displaced people and vulnerable residents in Lebanon with food and other items by the end of the year.
It aims to deliver drinking water to 1 million people and support health structures used by 600,000 people.