A schoolboy was taken to hospital after being stabbed in the leg.
Police were called to the shocking incident, which happened yesterday afternoon at around 3-10pm on the Swinden Playing Fields, in Cravendale Avenue.
It is believed that a group of teenage boys have approached the 13-year-old and tried to cause damage to his bicycle. During the altercation, the victim has received a knife wound to his lower leg and was taken to hospital for medical treatment. His injury is not thought to be serious.
Police said four boys aged 14 and 15 from Nelson and Colne have been arrested in connection with the incident.
They have since been released on bail pending further enquiries.
Police are appealing for witnesses, but are also reassuring the public that this is being treated as an "isolated" incident.
Det Sgt Richard Buckley, of East CID, said: “I know that incidents of this nature cause alarm, but I would like to reassure people that we are treating this as an isolated occurrence and do not believe there to be any wider concern for the local community.”
Anyone with information about the incident can call 101 quoting incident reference 902 of April 1st.