An Extinction Rebellion blockade at MOD Abbey Wood is expected to cause traffic disruption, say police.
Avon and Somerset Police has said specialist officers are dealing with the incident.
The scene of the protest is located near the roundabout with Great Stoke Way and could affect motorists around the retail park.
Just after 7am this morning, Avon and Somerset Police were alerted to "suspicious activity" at the Filton site.
An Avon and Somerset Police statement said: "Officers are at the scene of a protest at the MOD's Abbey Wood site in Filton following a call just after 7am today (Friday, December 11) reporting suspicious activity.
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"Protestors have blocked the entrances to the site with some claiming to be 'locked on'.
"Due to the proximity of the site to the A4174, roundabout junction with Great Stoke Way and retail park, there may be some traffic disruption while specialist officers deal with the incident."
More updates will follow on our live blog.
