Armed police have exchanged fire with a gunman after a person was shot in Oxford city centre.
Thames Valley Police said shots had been fired from a property in Paradise Square and officers returned fire. Police are currently negotiating with a man.
South Central Ambulance Service said one person was being treated for a non-life-threatening injury.
A cordon is in place around Paradise Square and Norfolk Road.
Firearms officers had been called at 13:15 BST after eyewitnesses reported hearing the sound of gunfire.
Supt Joe Kidman said: "People in Oxford will notice an increased police presence in the area while officers are dealing with the incident, which is contained and taking place at a residential property."
BBC reporter Will Banks said a helicopter was hovering over the scene, with at least 10 police vehicles on the ground and police activity centred on Paradise Square.
The Oxford Tube and Stagecoach said buses are not stopping on Castle Street.