Thousands of people are feared to have been killed in the areas of the Philippines hit by Super Typhoon Haiyan.
The country's Red Cross says it has been told there are 1,000 dead in Tacloban and 200 in Samar alone.
A Red Cross spokesman said: "We now fear that thousands will have lost their lives."
The scale of devastation led one UN disaster official to compare the destruction to that caused by the 2004 Indian Ocean tsunami.
The official death toll had reached 138 by 1pm on Saturday (UK time) but there are fears the eventual death toll will be "massive" after the tropical cyclone smashed through the country with winds gusting up to 170mph.
And there are growing fears for Vietnam which is now in the path of what has been called one of the most powerful recorded cyclones in history.
Sebastian Rhodes Stampa, head of a United Nations disaster assessment coordination team, said: "This is destruction on a massive scale.
"The last time I saw something of this scale was in the aftermath of the Indian Ocean tsunami."
Around 220,000 people died as a result of that disaster.
Gwendolyn Pang, Philippine Red Cross secretary general said: "An estimated more than 1,000 bodies were seen floating in Tacloban. In Samar, about 200 deaths. Validation is ongoing."
When asked how many had died in just the coastal town of Palo and its surrounding area, Energy Secretary Jericho Petilla said: "I think hundreds. Palo, Ormoc, Burauen... Carigara, they all looked the same."
Scores of towns and villages are thought to have been inundated with water after storm surges flooded low-lying areas, drowning many in their path.
TV pictures showed cars, trees and rubble from houses strewn across streets after they were picked up by giant waves and carried inland.
"Almost all houses were destroyed, many are totally damaged. Only a few are left standing," said Major Rey Balido, a spokesman for the national disaster agency.
About a million people evacuated because they were living in the typhoon's path have been returning to find out what is left of their houses.
Many of those who died are thought to have left shelters in an urgent bid to rescue valuables from their homes, unaware of the giant waves flooding through coastal towns.
Hundreds of thousands are thought to have been left homeless.
British team of humanitarian experts is due to fly out to the Philippines to help the UK Government decide what aid to send.
An appeal launched by the British Red Cross has already raised more than £100,000. US Secretary of State John Kerry said that America stood "ready to help".
Many of the most heavily damaged areas are still to be contacted because power and telephone lines are down, making the work of providing relief all the more difficult.
Captain John Andrews, a Philippines aviation chief, said he had spoken to colleagues by radio who had told him there were "100-plus dead lying on the streets" in Tacloban.
Tacloban is the capital of Leyte, a large island of about two million people that suffered a direct hit from Haiyan on Friday morning when the storm was at its strongest.
Leyte Island, about 350 miles south of the capital Manila, is one of six islands that was in the path of the super typhoon's centre.
An increasing problem for the authorities now is looting, with many of the survivors desperate to get hold of supplies from the shattered shops.
Thousands of police and army personnel are being flown into the affected areas to start relief operations and to uphold law and order.
At one point the super typhoon had been stronger than it was when it hit land, with winds gusting up to 235mph making it among the most powerful ever.
Meteorologists said that it had slowed to 100mph after passing over the Philippines but is still expected to be of typhoon force as it sweeps across the South China Sea toward Vietnam.
Hundreds of thousands of Vietnamese have been moved away from coastal areas as authorities prepared for Haiyan to make landfall around 10am Sunday. Millions are thought to be living in its path.
Sky News International Source