Two teenage boys were hospitalised after they were beaten with a crowbar by a masked gang of men.
The suspected paramilitary style attack occurred in the Iniscarn Road area of Londonderry on Thursday evening.
Detective Inspector Michael Winters said he believed a crowbar was used in the attack.
“At around 11pm, it was reported that a 17 year-old male was taken to hospital following an assault in a field in the area by a group of masked males.
"The man was treated in hospital for injuries to his legs which are not believed to be life threatening. It is believed that a crowbar was used during the incident."
D.I. Michael Winters added: “Shortly before 00:20am, it was reported that a 16 year old male received injuries to his legs believed to have occurred at the earlier incident at Iniscarn Road.
"The male was treated at hospital for injuries not believed to be life threatening.
“Enquiries are continuing to establish the circumstances surrounding this incident."
D.I. Winters condemned those responsible for carrying out the attack.
“Nothing gives these people the right to violate the human rights of people and their actions should be condemned by all.
"Those who are involved in paramilitary style attacks do not represent the interests of any community nor contribute anything to it.
"They do it to try and exert influence or gain control in communities.
“We would appeal to anyone who witnessed anything suspicious in the Iniscarn Road area between 10pm and 11pm last night to contact detectives at Strand Road on 101, quoting reference number 2247 29/08/19.
"Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime," said D.I. Winters.