The A303 has been closed eastbound in Hampshire while police deal with an ongoing incident.
The carriageway is shut between the A3057 at Andover and the A3093 at Picket Twenty, with motorists being warned to expect delays.
National Highways said Hampshire Police are leading the response to the incident.
No further details about the nature of the police operation have been released at this stage.
Diversion in place
Eastbound motorists are being diverted away from the A303 at the Hundred Acre interchange, before being directed through Andover using the A343 and A3093.
Traffic can then rejoin the A303 eastbound at the Picket Twenty interchange.
Drivers are being advised to allow additional journey time, consider alternative routes or delay their journey while the closure remains in place.
The duration of the closure is not yet known.
