A man has been shot by police at a house in Londonderry, the Police Ombudsman has said.
Police said they responded to "a report of concern for the safety of a man" in Celandine Court in Gobnascale at about 22:45 BST on Saturday.
The man was taken to hospital, where he is now understood to be in a stable condition.
A police officer also sustained knife wounds to his arm and head during the incident.
The Police Ombudsman's Office for Northern Ireland (PONI) was informed.
A spokesman for the PONI said: "Our investigators are at the scene and are making enquiries to establish the circumstances of what happened.
"At this stage, we know that police went to the flat after receiving a call for assistance.
"There was then a confrontation, during which one police officer sustained stab wounds and police discharged CS spray and a single gunshot."
In a statement, the PSNI said: "As officers were dealing with the incident, a police firearm was discharged and the man sustained a chest injury. A police officer sustained a knife wound to his arm and head during the incident and he was taken to hospital for treatment."
Sinn Féin MLA Martina Anderson said she was "deeply shocked" by the incident.
"The man is in intensive care in hospital and my first thoughts are that I hope he will survive his injuries," she said.
"Thankfully the police officer has been released from hospital and I hope he too makes a full recovery.
"I have contacted senior police and the Police Ombudsman to convey my grave concerns that lethal force has been used in this incident."
SDLP leader Colm Eastwood tweeted: "Worrying news that a man was shot and a police officer injured in Gobnascale last night. The Police Ombudsman needs to carry out a thorough investigation into this incident."