Hundreds of people are feared dead in the Philippines after Typhoon Haiyan swept through on Friday.
Among the worst hit areas were the eastern island of Leyte and the coastal city of Tacloban, which has seen buildings flattened and trees uprooted.
First reports said 100 bodies had been found but the Red Cross later said the figure could be more than 1,000.
Reports suggest another 200 may have died in Samar province, the Philippine Red Cross said.
Typhoon Haiyan - one of the most powerful storms on record to make landfall - is now bearing down on Vietnam, where tens of thousands are being evacuated from its path.
The Philippines' Energy Secretary Jericho Petilla flew to Leyte by helicopter and viewed the devastated fishing town of Palo.
He said he believed "hundreds" of people had died just in that area.
Gwendolyn Pang, secretary general of the Philippine Red Cross, said it had received preliminary reports by Red Cross teams in Tacloban and Samar.
She told Reuters news agency the teams had seen "more than 1,000 bodies floating in Tacloban".
"In Samar, about 200 deaths. Validation is ongoing," she said.
Video from Tacloban showed it engulfed by a storm surge.
The airport has been badly damaged and only military flights are able to operate, the BBC's Jon Donnison reports from Manila.
John Andrews, deputy head of the Civil Aviation Authority, said he had spoken to Tacloban's airport manager, who had seen more than 100 bodies around the facility and at least 100 more people injured.
The airport terminal had been "ruined'' by storm surges, he said.
Local TV journalists said they had seen 20 bodies in a church in Palo, 10km (six miles) south of Tacloban.
Sebastian Rhodes Stampa, head of a UN disaster assessment co-ordination team, said there was "destruction on a massive scale" in Tacloban.
"There are cars thrown like tumbleweed and the streets are strewn with debris. The last time I saw something of this scale was in the aftermath of the  Indian Ocean tsunami."
Communications to some of the worst-hit areas were cut off when the storm hit and it may be days before the final death toll and the full extent of the damage is known.
As darkness fell on Saturday, many areas were without electricity.
Jim Pe, deputy mayor of Coron town on the island of Busuanga, said most houses and buildings there had been destroyed or damaged.
Speaking by phone, he said five people drowned in the storm surge and three others were missing.
"It was like a 747 [jet] flying just above my roof," he said.
The storm made landfall shortly before dawn on Friday, bringing gusts that reached 379km/h (235 mph), with waves as high as 15m (45ft), bringing up to 400mm (15.75 inches) of rain in places.
Schools and offices were closed, while ferry services and local flights were suspended.
Haiyan also battered Cebu, the country's second largest city, with a population of 2.5 million.
The eye of the storm - known locally as Yolanda - passed well to the south of the capital Manila, but the city still felt its force.
In the typhoon's path were areas already struggling to recover from a deadly 7.3-magnitude earthquake last month, including the island of Bohol, where about 5,000 people are still living in tents.
Britain's ambassador to the Philippines, Asif Ahmad, said on Saturday that a team of humanitarian experts would be sent by the UK "to assess needs and then mobilise resources".
The head of the EU's delegation to the Philippines, Guy Ledoux, had earlier told local media that the EU was also sending a humanitarian aid team.
Internet giant Google produced an interactive crisis map showing evacuation shelters, command posts and medical centres.
Officials had said more than 12 million people were at risk.
The typhoon is now heading for Vietnam and is expected to make landfall on Sunday.
Authorities there have begun the mass evacuation of more than 200,000 people.
State media report that schools are being closed and people living in low lying coastal areas are being moved to typhoon shelters on higher ground. Shipping has also been ordered back to port.
Some 170,000 soldiers have been mobilised to provide emergency relief.
Two other typhoons - Wutip and Nari - have hit central Vietnam recently, causing widespread damage.
Michael Annear, Red Cross representative for Vietnam, told AFP: "Typhoon Haiyan is two or three times more powerful... We're expecting a lot of wind damage... especially for those who repaired their houses themselves after Wutip and Nari." (BBC)