Many villagers from the northern Manaseer area are refusing to leave their river-side farms and homes to make way for the Chinese-built dam designed to double Sudan's electricity supply.

The dam, which is due to start generating power by the end of the year, will flood a large part of the surrounding area 350 km (220 miles) north of Khartoum.

Hashim Ali, spokesman for a committee representing the Manaseer villagers, told Reuters more than 1,000 families on four islands in the Nile were stranded without food and shelter on Tuesday morning.

"Right now parts of the islands are being submerged ... Farms near the river have been destroyed. They are fighting the water. The people have had to go to higher ground on the middle of the islands," he said.

He said villagers had been left without help as local authority offices were closed on Tuesday, the first day of the Eid holiday marking the end of the Muslim Ramadan fast.

"They (the dam managers) have chosen this day to commit this crime. The officials are off and no one will hear us," he said.

Tens of thousands of other villagers have already been displaced by the dam project, but the Manaseer villagers are refusing to move saying houses built for them by the government are too far from the river and would not have the water needed to sustain their agriculture.

Ali said waters started rising on Sunday when managers closed the gates to test Merowe dam, around 100km (60 miles) downriver from the islands, and floods had peaked in the early hours of Tuesday morning.

But a spokesman for the Dams Implementation Unit dismissed the accusations. "The gates have not been shut. This area floods every year," he said.

The spokesman added that other villagers who had agreed to move had already started harvesting crops in their new locations. The local authority would have the responsibility of dealing with any people who refused to move, he added.

Access to the entire area is tightly monitored by the Dams Implementation Unit which reports directly to the presidency.

Police have killed protesters in Merowe in the past and arrested journalists going to the region to report. (Editing by Dominic Evans)