Hacker group Anonymous, in an embarrassment for law enforcement, released a recording Friday of a conference call between the FBI and Scotland Yard discussing operations against the hacking collective.

The Federal Bureau of Investigation confirmed the authenticity of the nearly 17-minute recording posted on YouTube and other sites and said it was "intended for law enforcement officers only and was illegally obtained.

"A criminal investigation is under way to identify and hold accountable those responsible," the FBI said in a statement.

The release of the audio recording was one in a series of attacks on Friday by the shadowy loose-knit group of international hackers.

Members of Anonymous also attacked the website of the Greek justice ministry in a protest against the country's tough fiscal reforms and a site operated by the Boston Police Department.

In addition, members of the hacker group defaced the website of the law firm that defended a US Marine who faced charges in connection with the 2005 killing of 24 Iraqi civilians.

Anonymous, in a statement on the website of the law firm of Puckett and Faraj, also claimed to have published online three gigabytes of private email messages of attorneys Neal Puckett and Haytham Faraj.

Puckett served as a lawyer for Staff Sergeant Frank Wuterich, who faced a court martial last month in connection with the killings in the Iraqi town of Haditha.

Wuterich, 31, admitted one count of negligent dereliction of duty but manslaughter charges were dropped as part of a plea deal with prosecutors and he is not serving any jail time.

Along with the FBI-Scotland Yard audio recording, Anonymous posted online the January 13 email invitation from an FBI agent setting up the call for January 17.

The email invites members of European law enforcement agencies to take part in a conference call "to discuss the on-going investigations related to Anonymous, Lulzsec, Antisec, and other associated splinter groups."

The email was sent to law enforcement officials in Britain, France, Ireland, Germany, the Netherlands and Sweden but the only people who identify themselves on the call are from the FBI and Scotland Yard.

The email includes the number to be called along with the access code.

In a message on Twitter, Anonymous posted links to the audio recording and said the FBI "might be curious how we're able to continuously read their internal comms for some time now."

According to the FBI, no agency computer systems were breached in connection with the incident.

Graham Cluley of computer security firm Sophos said the hackers were apparently able to access the call "because they have compromised a police investigator's email account."

"No doubt the police authorities will be appalled to realize that the very people that they are trying to apprehend, could have been tuning in to their internal conversations," Cluley said in a blog post.

During the call, the British and American participants discuss some of the targets of their operations including Jake Davis and Ryan Cleary, two British teenagers who were arrested last year over hacking.

Other names mentioned during the call are bleeped out.

Davis is charged with hacking into websites, including that of Britain's Serious Organised Crime Agency, which was out of service for several hours on June 20 after apparently being targeted.

Cleary was detained in connection with a month-long global rampage last year by the Anonymous splinter group Lulz Security.

At one point in the call, a British participant thanks his American counterpart for helping out with an examination of Cleary's hard drive.

Later, a British participant mentions a hacker from West Midlands who goes by the handle "tehwongz."

"He's a 15-year-old who's basically just doing this all for attention and a bit of an idiot," he said, going on to describe him as "a pain in the bum."

Last month, Anonymous briefly knocked the FBI and Justice Department websites offline in retaliation for the US shutdown of file-sharing site Megaupload.

In late 2010, Anonymous attacked the websites of Amazon, Visa, MasterCard, PayPal and others in retaliation for their decisions to stop working with Julian Assange's anti-secrecy site WikiLeaks.