A street in the centre of Oxford is in lockdown after armed police exchanged fire with a suspected gunman in a residential property.
Police were called to Paradise Street, just yards from Oxford castle, following reports that a man had a gun.
Armed response officers arrived at the scene and shots were fired from the property causing police to return fire.
The surrounding area was sealed off and members of the public were told to stay away while trained negotiators attempted to resolve the situation.
The incident, which began at 1.15pm on Monday, is ongoing as officers try to resolve the situation.
South Central Ambulance Service NHS Foundation Trust said on Twitter that one patient is being assessed and treated for “non-life threatening injuries”.
Eyewitness described hearing the gunshots ringing out during the afternoon. There were reports the suspect was shooting from a balcony.
Janet Borgerson was in the nearby Hotel Malmaison when she heard “explosive cracks” she thought were holiday festivities before another series of “loud bangs”.
“Again, I thought the second round were firecrackers. I noticed hotel bar staff ushering people inside,” she said.
Ms Borgerson, who is visiting the city from America, said guests were later told they were “perfectly safe” and allowed to leave the hotel by an armed officer who seemed to indicate he was expecting a siege.
A nearby resident, who did not want to be named, said he first heard two loud bangs early in the morning, but thought it was just Bank Holiday fireworks.
Later that day, he said he witnessed the start of the altercation between an armed man and the police, during which he heard around 20 shots exchanged.
He said: “I could hear a female negotiator and an armed response man trying to get him to put his hands up, let go of the gun, keep his hands on show and things like that.”
The resident said he heard a man repeating that he needed medical treatment, before getting “really angry, shouting, roaring at them (the police)”.
He said the whole street had been evacuated and families were getting anxious about where they would be able to spend the night as darkness fell.
A spokesman for Thames Valley Police said: “Our officers remain in Oxford city centretonight working to resolve the ongoing situation.
“Armed response officers are still present at a residential property in Paradise Square following a report shortly after 1.15 pm on Monday that a man had access to a firearm. Shots were fired from the property and police returned fire.
“Officers are continuing to negotiate with the man as they work to attempt to safely resolve the situation.
“Paradise Square and Paradise Street and part of Norfolk Street remain closed, which is likely to have an ongoing impact on people travelling in to the area tomorrow, and to local bus services. No buses are able to run from Norfolk Street.”
Superintendent 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.”
The incident is not being treated as terrorism.