WASHINGTON (Reuters) - Two New England men accused of plotting to behead Massachusetts police officers in support of the militant group Islamic State in Iraq and Syria (ISIS) were receiving instructions from one of the group's cyber experts, according to a new indictment released on Thursday (April 21).

A grand jury in federal court in Massachusetts added conspiracy to commit acts of terrorism transcending national boundaries to the charges against David Wright, 26, of Massachusetts, and Nicholas Rovinski, 25, of Rhode Island.

According to the new indictment, Rovinski has continued to support ISIS while in jail by trying to recruit others to "decapitate non-believers" and take down the United States government and by writing a new pledge of support to the group's leader, Abu Bakr al-Baghdadi, on the back of his own criminal complaint.

Rovinski and Wright pleaded not guilty to the original charge of conspiring to provide material support to a designated terrorist organization after they were arrested in June, and they were due to face trial in February 2017.

According to the new indictment, Rovinski and Wright plotted their attacks with Wright's uncle, Usaamah Abdullah Rahim, who was shot dead by law enforcement officers last June when Boston police and agents for the Federal Bureau of Investigation approached him and he threatened them with a knife.

The indictment accused Rahim of beginning communication one month before he was shot with a British member of ISIS, Junaid Hussain. Hussain was believed by government sources to be the leader of CyberCaliphate, a hacking group that last year attacked a Twitter account belonging to the Pentagon.

The indictment said Hussain gave Rahim instructions that Rahim passed on to Wright about targeting individuals such as Ms Pamela Geller, organiser of a "Draw Muhammad" cartoon competition in Garland, Texas, that was attacked by two gunmen last May.

Hussain was killed in a US drone strike in Syria last August.

Wright has pleaded not guilty to charges he alone faced of obstructing justice and conspiring to obstruct justice after he was accused of instructing Rahim to delete his phone and laptop data.

Wright and Rovinski now face maximum sentences of life in prison as a result of the new charges announced on Thursday.

They are scheduled to be arraigned on April 28, according to the docket report in their case.