A man has been arrested on suspicion of murder after three people were killed in the city.
Others are being treated in hospital following the incident in the early hours of Tuesday morning.
Police were called to Ilkeston Road just after 4am where two people were found dead in the street.
Officers were then called to another incident in Milton Street where a van had attempted to run over three people; they are currently being treated in hospital.
A man has also been found dead in Magdala Road.
Police have arrested a 31-year-old man on suspicion of murder and he remains in police custody.
Chief Constable Kate Meynell said on the Notts Police website: “This is an horrific and tragic incident which has claimed the lives of three people.
“We believe these three incidents are all linked and we have a man in custody.
“This investigation is at its early stages and a team of detectives is working to establish exactly what has happened.
“We ask the public to be patient while inquiries continue. At this time, a number of roads in the city will remain closed as this investigation progresses.”
All tram services have been suspended and Victoria Bus Station has been closed but the Victoria Shopping Centre remains open, and various roads remain closed across the city.
The following roads are currently closed: Ilkeston Road, Milton Street, Magdala Road, Maples Street, Woodborough Road from junction of Magdala Road into the city, Maid Marian Way junction of Parliament Street.
Joseph James, a student at NTU who also lives in Nottingham said: “I think above all it gives you a shock – I never expected something like this will happen in your city until it does.
“We can all pretend not to think about it, but after this incident it will play on my mind as I’m walking around in the future, when it happens in the streets you’ve walked around all your life, you can suddenly feel the weight of such a horrific event when it’s so close to you.”
If you have any information or are concerned about a family member or friend you can call this dedicated line – 0800 0961011.