William Reeve with the latest pictures

As they continue to evacuate the injured by helicopter, the full extent of the devastation is becoming apparent. Local authorities say around 4,000 people are thought to have died. Up to 60 villages have been completely flattened.

WHO's Dr Mohammed Jamma: "Area is endemic for malaria"

The continuing tremors add to rescuers difficulties and as every day goes by the dangers of disease increase.

A United Nations spokeswoman said the key to the rescue operation was to get shelter to the remaining survivors.

The International Red Cross is hoping to fly out all the injured within the next 24 hours, but the organisation's co-ordinator, Svante Yngrot, says much will depend on the weather.

UN's Sarah Russell from Islamabad: "Main problem is low cloud and inaccessability" (1'29")

A BBC correspondent who is in Faizabad, the town at the centre of the relief effort, says the international rescue effort is now in full swing, with piles of tents, tarpaulins and medical supplies building up at the local airport.

The United Nations aid co-ordinator, Alfredo Witschi Cestari, who toured the worst-hit provinces by helicopter, said thousands of people had lost their homes.

Pictures have begun arriving of the area affected by the quake

Some villages had been completely flattened, with houses shaken off mountainsides and sent crashing into the valleys.

A spokesman for the anti-Taleban alliance, which controls the region where the earthquake struck, told the BBC: "The number of dead is more than 5,000 and more than 2,000 injured. We expect the number will rise."

Aid workers say the area affected is remote and casualty figures should be treated with caution.

First pictures of the catastrophe

The earthquake - which measured up to 7.1 on the Richter scale - struck around the towns of Rostaq and Feizabad in an area close to the border with Tajikistan.

All transport by helicopter

All the transport in the quake area is by helicopter as the dozens of stricken villages are very remote. Mr Yngrot said he hopes each of the three helicopters will be able to reach up to 15 villages a day.

Thousands have lost their homes

He said Afghan doctors and nurses are taking care of most of the injured in the Red Cross clinics and local hospitals, not least because they speak the local language.

Special correspondent Ben Brown: "a region cursed by nature"

Aid workers are meanwhile assessing where relief assistance is most needed and exactly what supplies are required.

Mr Yngrot said the second phase of the relief operation will start on Wednesday. This will entail sending out tents, blankets, plastic sheeting and soap to the survivors.

Stronger than February quake

David McCauley, Merlin charity: "Population was just beginning to establish themselves" (3'10")

Relief workers say it was fortunate that the earthquake struck during the day when many people would have been outside their homes.

It was more powerful than the earthquake in the same area in February, which killed around 4,000 people.

In that quake, which occurred during the cold winter weather, the tremors were at night when most families were inside.

It also took two days before news of the February disaster reached the outside world, and then snow prevented the relief effort from getting off the ground properly.