A road has been sealed off amid reports of a police shooting.
The A369 was closed at Portbury, close to the M5 west of Bristol, Avon and Somerset Police said.
An eyewitness claimed he saw police shoot into a car that had been stopped. David Ellison told BBC Radio Bristol: "As I came out of Portishead to join the motorway I got stopped. Ahead of me were police in the road.
"I saw them back off from a car and then they surrounded it. They maybe shot with handguns five, six, maybe 10 times. Then they dragged a man from the car to resuscitate him."
An Avon and Somerset Police spokesman said: "We have closed off the Portbury 100 (A369) following an incident earlier this morning. The air ambulance has landed. Motorists will not be able to access Portishead from Junction 19 of the M5. We anticipate the road will remain closed for some time."
The Independent Police Complaints Commission said it had been notified of an "incident" by the force.