Police are investigating after pro-independence Yes signs in Moray were daubed with paint saying “Nae”.
Two field posters in Lossiemouth and another near Roseisle were vandalised within hours of being put up on Thursday afternoon.
The local SNP branch made a complaint to the police about the damage to the signs, which are worth about £12 each and funded through donations.
Officers issued an appeal for information about the incident last night.
Lossiemouth resident Carolle Ralph, who had allowed the signs to be put up outside her house, branded it “senseless vandalism”.
“By and large both sides have so far fought the campaign in a fair manner. I really hope that things remain positive,” she added.
Moray MP Angus Robertson described the damage as “very sad”.
He also welcomed the condemnation of the incident from both sides in the independence debate.
Sean Morton, Labour councillor for Fochabers Lhanbryde, said: “This is nothing short of vandalism. Yes Moray supporters don’t deserve it.”
Labour activist Duncan Hothersall said there was “no need for it”.
Graham Leadbitter, SNP councillor and secretary of the party’s Moray Constituency Association, contacted the police.
“Destruction of these signs is no different to vandalising anyone else’s property and this behaviour is entirely unacceptable,” he said.
“Freedom of expression is a precious right that must be protected for everyone involved in campaigning.
“So far the referendum campaign has been conducted in a fairly respectful way and with only seven weeks left of campaigning I really hope that it will continue that way.
“I have reported this criminal damage to the police who are investigating it and should any further vandalisms occur then they will also be reported.”
A police spokeswoman said: “Police have received a complaint about vandalisms in the Lossiemouth and Roseisle areas and inquiries are at an early stage.”