PARENTS and children have been put on alert after a sex pervert on a bicycle indecently assaulted a six-year-old boy.

The man has struck several times in incidents where he has exposed himself while riding his bike.

Burnley police say they are concerned he has now gone a step further and committed an indecent assault.

The cycling sex offender started with three incidents of indecent exposure to young boys.

His latest two offences are being classed as gross indecency and an indecent assault on the six-year-old.

Det Constable Nikki Butler said: "We are investigating five offences. They are increasing in their seriousness and we are concerned about what he might do next."

Schools and youth groups have been warned of the danger. Some schools have sent out letters to parents telling them of the concerns about the man.

The incidents have all happened in or near play areas in local parks and involve a man in "professional" cycling gear riding a mountain bike, predominantly red with black tyres and straight handlebars.

He is described as white, 25 to 35 years of age, slim, medium build, short dark hair and possibly with a moustache.

At each incident he has been described as wearing cycle clothing including black lycra shorts, a green/red and black cycling jacket and a predominantly red/blue cycling helmet possibly with a Raleigh motif.

On one occasion he was wearing a pair of red training shoes with a white sole.

Youngsters have told police he was carrying a black backpack with yellow, green and orange writing.

All the victims have been boys. An 11-year-old has helped police with an artist's impression.

Offences being investigated are:

Wednesday, February 21, about 3.40pm, indecent exposure in front of young teenagers playing tennis in Queens Park

Saturday, February 24, about 4pm, indecent exposure to young boys in Towneley Park

Sunday, March 4, 3pm, Towneley Park, indecent exposure to young boys

Thursday, March 15, 6pm, gross indecency, inviting young boys to join in an indecent act

Saturday, March 17, 6pm, indecent assault. Grabbed hold of the six-year old near Brunshaw Primary School who managed to escape and run off.