(CNN) Jeremy Hammond, the Anonymous hacktivist currently serving his seventh year behind bars, has been called to testify before a grand jury in the Eastern District of Virginia but does not plan to cooperate, a group representing him says.

The development is an indication the US Justice Department is exploring additional charges against WikiLeaks founder Julian Assange

In a statement, the Jeremy Hammond Support Committee said that "our assumption is that this the same grand jury that Chelsea Manning is currently being incarcerated for refusing to testify before."

Manning, a former Army intelligence officer who leaked a host of files to WikiLeaks in 2010, is currently jailed for refusing to testify before an Eastern District of Virginia grand jury, widely believed to be related to an investigation of Assange.

Hammond, 34, was anti-Iraq War protester who hacked a number of sites he believed were tied to the military industrial complex and governments that didn't respect human rights.

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