Kazakh President Nursultan Nazarbayev on Tuesday resurrected a Soviet plan by suggesting that Russia should divert Siberian rivers so that they flow into Central Asia.

"Why not recall a project to divert the flow of Siberian rivers into the southern regions of Russia and Kazakhstan as we discussed today and yesterday?" said Nazarbayev, speaking alongside his Russian counterpart Dmitry Medvedev.

"Over time, this problem may turn out very large (and) necessary to secure drinking water for the entire Central Asian region," Nazarbayev said at a regional summit in the Kazakh town of Ust-Kamenogorsk.

"Unfortunately today the issues of water security have been left without proper attention," he said, adding that the region's countries should join forces to secure water supply for the region.

The idea of diverting Siberia's north-flowing rivers towards the south was once very popular in the Soviet Union where scores of scientists worked on the plan which was eventually dropped.

Environmentalists say such a move would have catastrophic consequences but Moscow Mayor Yury Luzhkov has repeatedly floated the idea in recent years.

Russia and Kazkhstan are close allies and have taken steps to increase economic integration by building a single customs union.