Activists are trying to stop landowners clearing them from a "community garden" on waste ground in Brighton.
About 30 people have gathered at a site they have named The Mound, at the corner of Church Street and Portland Street in North Laine.
Security guards sent by Worthing-based landowner Hargreaves Property are understood to be trying to get onto the site.
This morning Sussex Police confirmed they were called at 8.45am by Hargreaves Property, who said they intended to clear the land.
The force said officers have attended to prevent a breach of the peace.
No arrests have been made.
The site has been vacant for 14 years.
Activists identified as a location for a new community garden after a project in Lewes Road was reclaimed by developers.