Three north bank machines were targeted by crooks trying to access customers cash cards at the weekend.
Card-skimming devices were found at ATMs in Inverness, Fort Augustus and Aviemore.
A member of the public spotted a suspicious device at the cash machine at the Great Glen Trade Centre in Fort Augustus, and the Inverness device was found on the High Street machine beside WH Smith’s store.
Both machines used the common method of fixing a minature camera above the keypad to capture the pin being typed in and also a fake card slot which has a reader inside that takes the details off the cards magnetic strip as they are put into the machine.
The cards are “read” and returned to the owner in the normal manner so the user may be unaware.
Police have advised anyone concerned that their details might have been stolen to check their accounts and contact their bank.
A force spokesman also said that detectives were looking at whether the three incidents were linked.
Inspector Ewan Henderson said: “Members of the public must pay close attention to see if there is anything unusual or suspicious about cash machines.
“To avoid being a victim there are several simple precautions to follow including checking the card reader and the front fascia for anything that appears to be out of the ordinary before inserting your card, and checking for any unusual attachments to the ATM, such as a leaflet holder.”
Anyone who finds any suspicious device or has any information regarding suspicious activity around cash machines is urged to contact Police Scotland on 101.