Commonwealth Bank chief Matt Comyn has conceded customers might be cynical about the latest spate of interest rate increases from three of the four major banks, but he maintained the hikes were justified by higher funding costs.

CBA and ANZ Bank joined Westpac by raising mortgage rates on Thursday, in a move that a leading analyst said underscores the "oligopolistic nature" of the country's big banks and will bolster their profitability.

CBA will increase mortgage rates by 0.15 percentage points, while ANZ said it would increase rates by 0.16 percentage points, in response to higher costs "as well as consideration of business performance and market conditions".

CBA chief executive Matt Comyn said the fact that CBA and ANZ hiked rates on the same day was "sheer coincidence". Credit:Peter Braig

The moves, which came within about 25 minutes of each other, followed Westpac's move last week to hike mortgage rates. They leave National Australia Bank as the only big four bank that has not yet moved.