More than 60 tons of aid, worth £500,000, was loaded onto two Russian charter planes at Stansted airport.

The BBC's Leon Hawthorne reports: "The medical supplies wil help treat the water and prevent the spread of disease"

The aircraft landed in Istanbul, where the supplies are being distributed to the worst-hit areas by international air forces.

It is the first major aid to be sent by the UK.

Blankets and communication equipment have also been sent, for the hundreds of thousands of people left homeless and injured.

The aid is vital to the survivors

Two communication experts were on the flights. They will join the dozens of British aid workers and specialists already helping with the emergency effort.

It had been hoped that the aircraft could land in some of the worst-hit zones, including the earthquake's epicentre Izmet, but the threat of more tremors meant it was too dangerous.

Unicef's Phillipe Heffinck: "The biggest problem now is dealing with injured and homeless people"

The confirmed death toll has climbed to more than 12,000, and there are fears that the final total could be as high as 45,000. Officials say the bodies of up to 35,000 people could still be trapped in the rubble of collapsed buildings.

Two Britons, Tom Blackwood, 65, from St Albans, Hertfordshire, and Lieutenant Commander Jim Acton, 37, based at Portsmouth, are among the dead.