An unprovoked park attack that left a teenager needing extensive surgery for stab wounds has sparked a police appeal.

A 15-year-old boy was found injured in Cassiobury Park, Watford, at around 5.45pm on April 28.

He was rushed to hospital by the ambulance service while Hertfordshire Constabulary scoured the area to find the attacker.

After evading police, the force launched an appeal describing the suspect as white, 5ft 10ins, around 17 years old, wearing a black puffer jacket and carrying a Flannels branded bag.

Detective Constable Vishal Khanna, who is investigating, said: “This was an unprovoked attack that left a teenager requiring extensive surgery. Thankfully, his injuries were not life threatening and he is now in a stable condition.

“We know that the park was very busy at this time on a Friday evening, and that it’s likely that many people would have witnessed the incident or any events leading up to it.

“If you did and have not yet spoken to police, it is vital that you do so – please get in touch with me as soon as possible.”

DC Khanna continued: “I would particularly like to speak to a group of teenage girls who were in the park near the area where this incident took place, as they could be possible witnesses with key information to help progress our investigation.

“There were five girls, who we believe to be around 16 years old, who were all wearing dark coloured tracksuits and trainers. If you think this may have been you, please get in contact.”

Anyone with information is asked to email vishal.khanna@herts.police.uk or call 101 quoting crime reference 41/34268/23.

On the evening of the attack, Hertfordshire Constabulary confirmed on their social media channels that they were still at the scene at 7pm, adding: “The incident happened close to the basketball courts and officers remain in the park at this time while enquiries are being carried out.”