Statistics Canada said the cost of living was unchanged from July, when the consumer price index also rose at an annual rate of 2.1 per cent.
However, core inflation, the number the Bank of Canada closely monitors and which excludes some items from the volatile energy and food categories, also rose by 2.1 per cent, after an increase of 1.7 per cent in July.
The central bank has set a target inflation rate at two per cent.
"Positive inflation numbers such as today's release could cause the Bank of Canada to get a little uncomfortable with their view on inflation and interest rates," said Rahim Madhavji of Knightsbridge Foreign Exchange in a note.
The BoC's next rate announcement is set for Oct. 22 when it is also expected to publish an update to its monetary policy report. It has kept its key rate at one per cent for the last four years.
The Canadian inflation data came on the same day referendum results showed Scotland will remain part of the United Kingdom.
Fifty-five per cent of Scots voted against independence, while 45 per cent voted in favour, providing relief for investors. The result avoided uncertainty in the U.K. economy and markets over the future value of the pound and public debt, among other things.
In commodities, the October crude oil contract on the New York Mercantile Exchange dropped 33 cents to US$91.65 a barrel, December gold bullion fell $10.30 to US$1,216.60 an ounce and December copper barely changed at US$3.09 a pound.
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