Leading international donor organisations have pledged $3 billion to help save the shrinking Aral Sea -- the worst man-made ecological catastrophe ever.

The funds will go to improve the socio-economic, health and ecological situation in Uzbekistan, Kazakhstan and Turkmenistan, the countries bordering the lake, officials said late Wednesday at the end of two-day international conference held in the north-western Uzbek town of Urgench.

The documents were signed between the International Fund for Saving the Aral Sea and the Uzbek government on the one hand, and a number of international organisations such as the World Bank.

"Today we are signing a package of documents worth $3 billion... to ease the consequences of the catastrophe that affects the livelihoods of 67 million people in the Central Asian region," Rustam Azimov, the first deputy prime minister of Uzbekistan, said during a signing ceremony.

Earlier UN chief Ban Ki-moon and Uzbek President Islam Karimov called on an international conference of experts and donors to come up with more aid to counter the devastation caused by the disappearance of the Aral Sea, which used to be the fourth largest lake in the world.

Seventy-five million tons of dust and toxic salts are blown annually into the atmosphere from the dried-up seabed, causing various diseases among the population, and the region has lost more than a half of the gene pool of its flora and fauna, according to officials.