LONDON, July 2 (Reuters) - Barclays was not an isolated case in the authorities' probe of banks rigging a key interbank interest rate, Britain's Financial Services Authority said on Monday.

"I wish I could say this was an isolated case... You will hear more on this in due course," the FSA's acting director of enforcement, Tracey McDermott told the watchdog's annual enforcement conference.

Barclay's behaviour was unacceptable to regulators and the public and a number of investigations were ongoing, McDermott said.

Barclays Chairman Marcus Agius quit on Monday, saying "the buck stops with me" after an interest rate rigging scandal dealt "a devastating blow" to the bank's reputation.

More than a dozen other banks are being investigated in the long-running global probe by authorities in North America, Europe and Japan, including Citigroup, HSBC, UBS and Royal Bank of Scotland. Analysts and bankers expect more big fines.