Bomb squad police in Australia are investigating three more blasts at automatic teller machines in Perth, making it six raids on suburban ATMs in 11 days.

The most powerful blast, which occurred at 3.30am this morning local time at a Westpac ATM in the northern suburb of Whitfords, punched a hole in the wall around the ATM and damaged internal walls.

Earlier attacks targeted a National Australia Bank ATM at Cockburn Shopping Centre in the southern suburb of Success at 1.40am (WST) and a BankWest ATM in nearby Canning Vale 20 minutes later.

Police won't say whether any cash was stolen.

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They are still investigating possible links between three recent attacks on ATMs in the southern suburbs of Secret Harbour, Willetton and Riverton, all involving a gas substance.

- AAP