The distance from the airport to the centre of town is just seven miles by road, but the journey can easily take six hours. To get to Tacloban, the small city in Leyte province in the Philippines that was flattened on Friday by typhoon Haiyan, you have to manoeuvre through piled-up bodies, uprooted trees, jagged pieces of debris and survivors staggering around searching for food, water and supplies.

The coastal city of 222,000 inhabitants bore the brunt of 195mph winds as the strongest storm ever recorded tore off roofs and destroyed evacuation centres.

Storm surges of up to six metres in height turned roads into rivers of sewage and seawater, landing whole ships on top of houses and obliterating bridges and roads. At least 10,000 people are thought to have died so far in Leyte province alone, with the toll expected to rise.

Without clean water, food or medicine, Tacloban's survivors have begun raiding houses, shops and malls to find supplies, with video footage showing residents scrambling out of a mall with electronic goods that they were probably hoping to barter for food.

One shop owner was photographed defending his premises with a pistol, while reports emerged of aid convoys being hijacked and cash machines being looted. Local officials warned the Philippine president, Benigno Aquino III – who visited Tacloban yesterday – that residents from nearby towns were entering the city to steal supplies and pleaded with him to declare martial law.

Even Tacloban's airport was reduced to a shell. But survivors, authorities and media all crowded into the building through ragged gaps in its walls.

The airport is both a makeshift command centre – from which the army finally began yesterday to deliver much-needed supplies – and the only way out for many survivors, who were queuing hundreds deep in an effort to leave the chaos behind.

More grimly, the airport has been turned into a makeshift morgue for the growing number of bodies, found stacked in churches, snagged on tree branches or underneath rubble. Mass graves have been dug to accommodate the corpses, with police chief Elmer Soria reckoning that most victims either drowned or were crushed to death by crumbling buildings.

"It was like a tsunami," said Philippine interior secretary Mar Roxas, who visited Tacloban yesterday by helicopter. "I don't know how to describe what I saw. It's horrific."

With communications still inoperative across vast swaths of the hardest hit areas, it was impossible to judge the scale of the destruction. Aid agencies warned they could not reach all those affected, with airports and harbours across the Philippines either closed or badly disrupted.

Emergency teams have been forced to try to reach survivors on foot, in many cases walking for hours over debris to access remote and ravaged areas.

Speaking from Samar island, Aya Lowe, who drove to Tacloban from Manila to assess the damage, said the roads in and out of the city were at a standstill. "We came across the main bridge towards Tacloban and there was just a huge traffic jam to come in or out," she said. "There were people coming in on mopeds and families trying to find their loved ones, and people coming out with boxes of shampoo and mayonnaise and random stuff."

But with the typhoon having swept across a number of cities – one Filipino official said the storm "island-hopped" – Tacloban is just one town among many that will have to be rebuilt from scratch. If the death toll is as high as is feared, Haiyan could emerge as the deadliest natural catastrophe in the Philippines' history.

More than 350,000 people were awaiting supplies in 1,220 evacuation centres, with 4.3 million people across the country affected by Haiyan, said Orla Fagan of the UN Office for the Co-ordination of Humanitarian Affairs (Ocha). She added that some areas were still 80% under water.

UN teams have been dispatched to the areas south and north of Tacloban and to Iloilo, to the west of Leyte and Samar islands, to assess the damage there. "We haven't been to the west of the Visayan islands yet so we have no idea what's gone on there," Fagan said. "We could be replicating what happened in Tacloban."

Another Tacloban native, Rochelle de Leon, said she was planning to fly from Manila to Cebu, then take a boat to Leyte island, where she would have to take a van and walk, carrying supplies. "I'll dress in camouflage so we won't get mobbed," she said by phone from Cebu. "I just want to know that my mum is OK. She was home alone when the typhoon hit and, well, I haven't heard anything since."

The typhoon was decreasing in intensity and had been downgraded to a category one storm by the time it made landfall in Vietnam last night, although gusts of up to 100mph were still being recorded.