Image caption Stratfor urged its members to notify authorities about any suspicious credit card activities

The activist hacker group Anonymous says it has stolen thousands of emails, passwords and credit card details from a US-based security think tank.

The hackers claim they were able to obtain the information because the company, Stratfor, did not encrypt it.

They say Stratfor's clients include the US defence department, law enforcement agencies and media organisations.

The Austin-based company says it has now suspended the operation on its servers and email.

An alleged member of Anonymous posted an online message, claiming that the group had used Stratfor clients' credit card details to make "over a million dollars" in donations to different charities.

Stratfor later announced that it would keep its email and servers suspended for some time.

It also said the disclosure was "merely a list of some of the members that have purchased our publications and does not comprise a list of individuals or entities that have a relationship with Stratfor".

Anonymous has previously claimed responsibility for cyber attacks on financial institutions seen as enemies of the whistleblowing website Wikileaks.