Police have cordoned off part of the town centre after an incident outside Kingston County Court.
Officers were guarding part of St James Road earlier this afternoon but the road has now re-opened.
A spokesman for London Ambulance said they had received a call to an incident at Kingston County Court at about 5.15pm.
A witness described seeing officers around a man on the floor who appeared to be injured.
An employee of Unilever who declined to give her name said a man came running out of court.
She said: "Security chased him out. He turned right. He bit a security officer on his arm.
"He got to the traffic lights and stopped because cars were there. He was looking for an escape. He saw a lady on a bike and grabbed it to try to get away.
"Security pulled the bike, lots of screaming and the officers grabbed the bike. There were fists everywhere. The security held him on the floor.
"He was hitting them."
A woman police officer appeared to have suffered an injury to her face.
Did you see what happened? Call the newsdesk on 020 8744 4244.