Disaster struck at a wildlife reserve when an estimated 10,000 litres of oil spilled into its waters.

Animal rescuers have been battling to save swans, moor-hens and terns that were overwhelmed by the slick which flowed into Pagham Rife and Pagham Harbour, west of Bognor Regis.

The Environment Agency and RSPCA officers were scrambled after reports of red diesel leaking from a nearby storage tank yesterday morning.

Gallons of the toxic fuel found its way through ditches and ponds to the rife and harbour, where it spread across the water surface, incapacitating birds as it swamped their feathers.

Dozens of birds have already been taken to the RSPCA's wildlife centre, near Hastings, where they can be scrubbed clean.

Environment Agency spokesman Ray Kemp said the spillage was disastrous.

"We are still investigating where it came from," he said. "It's a real wildlife reserve and this has caused a lot of damage quite quickly.

"We have a private contractor conducting a clean-up operation, they will try to suck a lot of it up where they can, because oil is lighter than water and it floats on the surface. But were it gets to the shore it will be messy."

There had been no reports of dead animals by the time darkness forced rescuers to stop their efforts last night.

Mr Kemp said: "Near the source of the pollution, a significant amount of diesel has been contained in a pond and stretch of ditch using dam boards. More oil is being contained nearer toward the harbour with booms."

Klare Kennett, of the RSPCA, said: "We have had to rescue several swans caught up in oil."