Westminster Bridge has been closed in both directions as officers respond to an ongoing incident.
Met Police were called to the area just before 4pm today following concerns for the welfare of a man.
Emergency services remain at the scene while diversions are in place.
A Met spokesperson said: "Police were called at 15:41hrs on Sunday, 18 October following concerns for the welfare of a man on Westminster Bridge.
"Emergency services remain at the scene and Westminster Bridge, along with a number of surrounding roads, has been closed while officers respond to the incident.
"Motorists and pedestrians are advised to avoid the area where possible."
When life is difficult, Samaritans are available day or night, 365 days a year. You can call them for free on 116 123 or visit samaritans.org.