Nato spokesman Peter Daniels said the closing of Yugoslav water pumping stations was a consequence of Nato's targeting of the electricity supply network.

"We have not targeted the water system ... we have targeted the transformers, and the edges so to speak, of the electricity generating system."

(Click here to see a map of the most recent reported air strikes)

Nato bombers again hit power facilities in Serbia overnight, causing further shortages of electricity and water throughout the country.

Water supplies were severely restricted in the Serbian capital and the northern city of Novi Sad.

Belgrade's water authority issued an appeal for people to cut consumption until supplies can be restored, and the state-run electricity company pleaded for patience.

"Every effort is being made to restore power supply to priority users to alleviate the humanitarian disaster being caused by Nato," the company said in a statement carried by Tanjug news agency.

One pro-government television station says 70% of Serbia is now without electricity and Belgrade is reported to be down to its last 10% of water reserves.

'Dozens' killed

Meanwhile, the Yugoslav authorities say dozens of people have been killed and about 200 injured by Nato's repeated bombing of Istok prison in Kosovo.

BBC's Jacky Rowland: "The visit raises more questions than it answers"

Prisoners are said to include Kosovo Albanian separatists.

The prison was first bombed overnight last Thursday.

BBC Belgrade Correspondent Jackie Rowland, who was taken by the authorities to visit the prison, counted more than 40 bodies, although it was not clear how many were Kosovo Albanians.

The authorities say the prison has only just been evacuated because overflying Nato aircraft made it too dangerous to move people earlier.

Nato has insisted the site is being used for military purposes and a number of questions about the prison remain unanswered.

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