Nanaimo Mounties are warning of an "alarming" spike in thefts from motor vehicles in recent months.

In September alone, the Harbour City saw 242 reported thefts from cars – more than double the number of thefts in the same period last year, when there were 113 reported thefts.

Police say there have already been 1,555 thefts from January through September this year, compared to 1,661 for all of 2017.

Nanaimo RCMP spokesman Const. Gary O'Brien said he expects thefts from cars will eclipse last year's number within two weeks.

"There are several factors which lead to increases in theft from vehicles and several key ways in which the public can assist in reducing this number," O'Brien said in a news release.

He's urging drivers to always lock their vehicles and keep valuables out of sight.

"Thieves will walk up and down streets, usually late at night, and as they pass a vehicle, grab door handles. If it’s locked they move on," he said, adding that 45 per cent of all vehicles broken into are unlocked.

Investigators are also encouraging the public to report all suspicious activity to them at 250-754-2345 or Crime Stoppers at 1-800-222-8477.