Police have taped off a road near Lincoln High Street due to an ongoing incident, with eyewitnesses reporting a stabbing on Vernon Street.
A man in his 20s has been taken to hospital following an assault. Police say he suffered injuries.
A reporter at the scene said residents have been evacuated from their homes.
Officers attended the scene just after 3.30pm. An air ambulance was also spotted circling overhead.
Eyewitnesses have claimed a person was injured with a blade.
There is also a partial road closure in place in the High Street area. This is affecting transport services in the city centre.