Aid workers struggling to help survivors of Typhoon Haiyan in the Philippines have described the situation as bleak, one week after the storm tore into the country.
A spokesman for Medecins Sans Frontieres said the logistical issues of distributing aid were enormous.
However, correspondents in the ruined city of Tacloban say US military aircraft are beginning to bring in aid.
Philippine officials say the death toll has now risen to 3,621.
Interior Secretary Mar Roxas said this figure was as of Thursday and the actual number was likely to be higher.
The Philippine's National Disaster Risk Reduction and Management Council said that there were a total of 2,360 confirmed deaths, while other reports from the ground put the figure higher than Mr Roxas' tally.
The discrepancy is likely to be due to the widespread devastation, making confirming casualties and collating information difficult.
Typhoon Haiyan was one of the most powerful storms ever recorded on land.
Henry Gray, of Medecins Sans Frontieres, said workers who had visited Guiuan, in eastern Samar, described the situation faced by the 45,000 people there as "bleak".
"What we saw there was that a public hospital had been, basically, destroyed," he said.
Mr Gray added that local officials had asked the charity to support a local private clinic.
"We are moving this as quickly as we possibly can, but the logistical issues are enormous and they shouldn't be underestimated," he said.
The BBC's Andrew Harding, reporting from near Guiuan, says that after earlier problems with looting, some supplies are now getting in.
As a huge international relief operation swung into action, aircraft carrier the USS George Washington and two cruisers arrived in Philippine waters on Thursday.
The carrier is expanding search-and-rescue operations and providing a platform for helicopters to move supplies.
The US military says its support will be on an unprecedented scale, with other US vessels due to arrive in about a week.
Pallets loaded with food and water have been taken from the aircraft carrier to Tacloban, the capital of badly hit Leyte province, and Guiuan.
Sebastian Rhodes Stampa, head of a UN disaster assessment team, said: "There is a danger of focusing on Tacloban."
"We need to get [aid] out to other parts of Leyte and Samar as soon as possible... we'll be here for some time to come."
Many of the dozens of bodies lying in the open since Typhoon Haiyan struck are now being cleared from the streets and buried.
Despite the relief effort, thousands of survivors continued to line up at Tacloban's airport on Thursday trying to leave the city.
A BBC correspondent at the scene said there was still no large-scale food distribution taking place.
But on Friday Mr Roxas, the interior secretary, defended the government's relief efforts.
"In a situation like this, nothing is fast enough," he said. "The need is massive, the need is immediate, and you can't reach everyone."
Mr Roxas, who is overseeing the response, said with roads blocked and infrastructure destroyed it had been hard to get relief supplies out to those in need.
He said he only had eight trucks for the entire city of Tacloban and its population of almost a quarter of a million.
Many countries have pledged help in the shape of financial aid, relief supplies or emergency teams.
The UK government is sending the aircraft carrier HMS Illustrious, more than £20m ($32m) in aid, a team of medical experts and an RAF transport aircraft.
Japan is also preparing to send up to 1,000 troops as well as naval vessels and aircraft. On Friday, it pledged a $40m (£25m) disaster-relief grant to the Philippines, in addition to an earlier $10m pledge, Japanese media reported.
China - which is engaged in a territorial dispute with the Philippines - is sending 10m yuan ($1.6m; £1m) in relief goods.
Its initial pledge of $200,000 (£120,000) from the government and Chinese Red Cross combined drew criticism in US media, but was also condemned by some Chinese internet users as excessive.