This follows the arrest of four criminals who entered the Scottish Borders on Monday evening after committing crimes in other areas.
A Police spokesperson said: “It is often convenient to place mobile phones on tables when in a café, restaurant or other public place. We can then become distracted by other things.
“Criminals will take this opportunity to steal phones and other valuables without the owner realising.
“While crime in our area is low we cannot become complacent.
“This is highlighted by this incident of criminals entering the Scottish Borders from outwith our area.”