Staff in the bank have been moved to safer sections of the building, while workers in nearby offices have reportedly been told to stay away from the windows of their premises.
A Bank of England statement said: “Following reports of a suspect vehicle near the Bank of England, the bank has moved staff to safe areas of the building.
“All essential operations continue from those areas.”
A City of London police spokesman said: “We are dealing with a suspect vehicle at Bank Junction, all roads leading from the junction have been closed while we deal with the incident.
“Bank station is closed to Central and Northern line trains only while we respond to a security alert.”
@LexiBoddy said earlier on Twitter: “Guy in car with music blaring. Runs red light. Stops car in intersection & walks off. Police everywhere. Bank station.
"I called it in to police to describe him. When I left they were creating road block and putting up tape to stop people walking by!"