Travellers have set up camp on city council-owned land at Salt Ayre Sport Centre.
The group arrived earlier this week, and council officers have given them notice to leave the site.
A council spokesman said: “We are aware of an unauthorised encampment on land which is owned by the council at Salt Ayre Sports Centre.
“Notice has been given that any persons occupying the land without the consent of the council are required to vacate the site no later than 1pm on Saturday July 4.
“Failure to comply with this request will result in the city council commencing legal proceedings to regain possession of the land.”