DETECTIVES today stepped up a hunt for a naked man wearing only a cycling helmet who confronted three children on a playing field in Nelson.

Det Sgt Michael Collins warned that it was important to catch the sex pervert before something else happened.

The children, a boy of 11 and girls aged 12 and 13, were playing at Swinden Hall playing fields when they were confronted by the man.

He grabbed one of the terrified girls who managed to break free.

All three escaped by wading across a shallow river and running off towards Cravendale Avenue.

Their ordeal began at 8.30pm on Wednesday when a man riding a red mountain bike rode passed them.

At that time he was wearing a red T-shirt and black jacket. A short time later -- and now wearing nothing but a white and black helmet -- he approached them on foot.

He made a grab for one of the girls, who managed to escape.

The children ran home and police were warned. Last night police were making a widespread search of the area and carried out house to house inquiries.

Police are also studying previous sex offences to see if their may be any link.

The man is described as white, early 30s, slim with a dark moustache.

Two of the children have told police they believe they have seen him before in the area.

DC Dean Holden said: "We are obviously very concerned about this incident.

"The indecent exposure is serious enough, the children describe him as playing with himself as he approached them.

"He made a grab for one of them and needs to be caught before something else happens."

DC Holden said they were asking for help for the public.

They wanted to know whether there had been any other incidents which had not been reported for any information.

Anyone who knows the man or who can provide any information is asked to contact either DS Collins or DC Holden at nelson CID on 01282 472645.