People with second homes and campervans have been reportedly travelling in large numbers to the area in recent days.
Mr Ewing said: “I am furious at the reckless and irresponsible behaviour of some people travelling to the Highland and Islands. This has to stop now. Let me be crystal clear, people should not be travelling to rural and island communities full stop. They are endangering lives. Do not travel.
“Panic buying will have a devastating impact on the livelihoods of rural shops and potentially puts unwanted pressure on NHS services in our rural communities.
“The Scottish Government’s advice is that essential travel only should be undertaken. We have been in touch with CalMac and industry leaders to discuss what further measures may be required to deal with this issue.”