A giant fish which has attacked swans at a bird sanctuary has been spotted by wildlife experts.

At least two swans have been hurt by the underwater creature nicknamed the Monster of Martin Mere which hides in a lake in West Lancashire.

Now a four-man team says it has located the attacker which they think could be a Wels Catfish from eastern Europe.

Although the biggest ever caught was 16-feet long, Jonathan Downes, one of the team from the Centre for Fortean Zoology in Exeter, thinks this one is a tiddler by comparison - perhaps seven feet long and weighing 24 stone.

The mere is home to scores of swans

He said: "If it is a Wels, it is almost certainly a British record."

The team is spending four days at the Wildfowl Trust at Martin Mere using infra-red cameras, military-style night lights and sonar equipment to find out more about the mystery beast.

The giant fish was first spotted on Thursday by team member Richard Freeman who is hoping to capture the creature on film.

He said: "I have seen something black and shiny snaking around in the water in almost the same place as the original sighting several months ago.

"It certainly looked like a Wels catfish.

'Rubbery' body

"However we will be carrying out further investigations over the weekend in hope of obtaining photographic proof".

Mr Freeman said the fish had no scales, had a "rubbery" appearance, was oily-black in colour and moved quickly through the water.

"I can't say for sure that it was a Wels catfish. But if a pike had attacked the swans there would have been wounds.

"This thing seems to come up underneath and drag its prey down under the water."

Reports of a larger-than-life creature living in the 17-acre lake were first voiced four years ago and the Martin Mere monster has since become a talking point among people living near the 380-acre reserve which regularly attracts Whooper and Bewick swans.