Police in the North expect to make more arrests after a Real IRA rally in the City Cemetery in Derry on Easter Sunday.
Scores of republicans were pictured listening to a statement by a masked man organised by the 32 County Sovereignty Movement - seen as the Real IRA's political wing.
Video footage from the cemetery showed the Real IRA declaring police officers would be targeted "regardless of their religion, cultural background or motivation".
Veteran republican Marian Price - also known as Marian McGlinchey and dubbed the "Old Bailey bomber" after she was convicted of a 1973 bombing outside the London courthouse in which one person was killed and almost 200 others injured - was quizzed by PSNI officers after appearing at the rally.
She was later charged with encouraging support for an illegal organisation and her licence was revoked, sending her back to prison.
Price is accused of addressing a meeting encouraging support for a proscribed organisation, the Real IRA, by holding the piece of paper from which the balaclava-clad spokesman read.
Northern Ireland Secretary Owen Paterson told MPs today: "The police investigation into those shocking scenes at Easter took its course and charges were laid against Marian McGlinchey.
"I took the decision to revoke her licence as she was charged under the Terrorism Act.
"I spoke to the chief constable this morning. Police investigations continue and I am confidence the PSNI will bring further charges forward when they have sufficient evidence."
Speaking at Commons questions, shadow Northern Ireland secretary Shaun Woodward said Monday's bomb scare in central London showed nationalist splinter groups still wanted to disrupt everyday life on mainland Britain and in the province.
The DUP's Ian Paisley welcomed the decision to revoke Price's licence and expressed concern that magistrates originally granted her bail after her first court appearance.
He said: "What sort of message does that send out by our courts of the softly-softly approach they seem to have when it comes to confronting dissident republican terrorists?"
Mr Paterson went on to admit hardline terrorists in the North were still trying to hit targets. "They are continuous in their efforts to attack not just the police but completely innocent members of the general public going about their day-to-day business.
"Although we think they are small in number, they do have capability and we do not underestimate the threat." He added.