The scale of the devastation caused by Turkey's massive earthquake has become apparent with a prediction by a senior UN official that the final death toll will reach 40,000.
Up to 35,000 people are still buried under the rubble, according to Mr Sergio Piazzi, head of the European desk at the UN office for the Co-ordination of Humanitarian Affairs.
However, hopes that large numbers of these victims could still be pulled out from the wreckage of their collapsed homes were fading fast yesterday, amid further criticism of delays in the relief operation.
Medical teams are now seriously concerned about the possible spread of cholera, dysentery and other diseases in the worst-affected towns in north-eastern Turkey, where the stench of rotting corpses has grown stronger by the day.
Stricken towns such as Golcuk and Izmit have no running water, no power supply and no refuse collection. Tens of thousands of homeless families, and many more too frightened by the threat of further tremors to return to their homes, have just spent a fourth night sleeping in the open in appalling conditions.
Members of rescue teams have been immunised against the main infectious diseases, and protective face-masks have been issued to rescuers and townspeople alike.
The Turkish Prime Minister, Mr Bulent Ecevit, described the risk of epidemic as "the greatest problem now facing us". The government was considering spraying buildings with disinfectant to prevent the outbreak of disease.
The Health Minister, Mr Osman Durmus, said five teams had been dispatched to the worst-hit areas to collect refuse, put more chlorine in reservoirs and pick up dead bodies.
There is also growing concern about remote rural areas hit by the earthquake, where the damage has not been assessed by the authorities.
Mayors in several small towns have sent videos of the devastation in their areas to Turkish television stations, in an effort to spur the government into action.
The official death toll from Tuesday's earthquake now stands at over 10,000, with some 34,000 injured.
Journalists and aid workers reported further chaos in the rescue operations yesterday as traffic jams and a lack of co-ordination caused major problems.
The Ankara chamber of commerce complained it had sent three tonnes of food supplies to the quake zone but no one could be found to distribute the items to the public.
Under pressure from critics who say his government's response has been inadequate, Mr Ecevit yesterday described the quake as "one of the worst disasters in the history of humanity, to my knowledge - the worst that Turkey has known," he said.
The governor of the country's central bank, Mr Ghazi Ercel, put the cost of the quake to the Turkish economy at $5 billion to $7 billion.
Mr Piazzi said he believed some victims trapped in open spaces between concrete slabs of collapsed buildings could survive until Monday or even Tuesday. Even yesterday, there were rare miracles as, for example, when a three-year-old girl was brought out alive from a crushed apartment block in Izmit. Doctors said she was severely dehydrated but otherwise unhurt.
An 11-year-old girl buried alive beneath the debris was rescued in the western town of Cinarcik by Israeli soldiers, according to an Israeli army statement.
There are now 2,000 search-and-rescue specialists and 120 sniffer dogs, sent by two dozen countries, in Turkey to help local rescue workers. However, delays in their arrival and deployment may have cost the lives of many of those buried under the rubble.
Speaking at a press conference in Geneva yesterday, Mr Piazzi said his forecast of the final death toll was based on Turkish government estimates. These in turn were based on aerial surveys of the thousands of damaged buildings matched against population density figures.
He pointed out that one-third of Turkey's population of some 63 million lived in the areas affected by the quake. The government had requested 10,000 body bags, as well as cranes and other heavy lifting equipment, he added.
Most of Istanbul's inhabitants spent Thursday night in the open, after state-run television carried warnings that further tremors were imminent. Many will continue to sleep outside this weekend.
President Demirel was accosted by angry residents complaining about insufficient relief efforts when he visited north-west Turkey yesterday. "Do not rebel against Allah in the face of an event sent by Allah," he told them, according to the Anatolia news agency.
"We are Muslims. We will wait for the solution from Allah as well . . . It is not possible to know what happens underground . . . If we believe this is the will of Allah, then we will have no trouble understanding the event," he said.