Update: The caravans vacated the park on the morning of Saturday, October 1.
Groups of caravans have set up pitch at Hartsolme Park in Lincoln.
Police have attended the scene to speak with the travellers, who are said to have arrived at around 3.30pm on Friday, September 30.
Members of the public are manning the entrance to the park to stop any additional caravans and motorhomes from entering the site and parking illegally.
A spokesperson for City of Lincoln Council said: “We are aware travellers arrived at Hartsholme Country Park this afternoon (Friday, September 30).
“We are liaising with the police and county council and, if appropriate, we will be taking action in accordance with the Joint Protocol on Unauthorised Encampments in Lincolnshire.”
This is the second time in two months that caravans have been pitched illegally on the site.
The car park had been closed to members of the public in August to stop unauthorised access.