Travellers have set up in the field next to the play park on Woodville Road in Boston.
It is understood they arrived last night (Monday) and were reported to have been previously moved on from an area in Lincoln.
It is also understood they are unrelated to the caravans which generally tend to arrive for the May Fair andstarts this week.
A spokesman for the council confirmed the authority would be asking them to leave.
They added: “Depending on the response we get we may have to begin the legal process required to get them to leave.”