Owners of small dogs have been warned to keep their pets on a lead after a woman said she spotted a 6ft snake in an Essex wood.

Basildon Council has put up posters in the Norsey Wood nature reserve near Billericay including a picture of the boa constrictor.

"It is apparently not a danger to humans, but it would probably be a good idea to keep small dogs on a lead," it reads.

But Daniel Hepplewhite, a reptile expert from Snakes Alive, said the reptile was unlikely to attack dogs.

"It will be more interested in squirrels," he said. "It's an arboreal species, so it's probably up a tree."

Mr Hepplewhite, 37, said the boa constrictor has not been sighted for three weeks but could survive in the British climate until the winter.

"A lady phoned up a few weeks ago saying she saw a snake heading into the woods," he said.

"She sent a picture, which is the picture on the poster."

The snake is thought to be an escaped, or illegally released, pet.

Mr Hepplewhite suggested the owner may have come back to find it or the sighting may have been a hoax.