PSNI chief constable Hugh Order has played down claims that security measures were too relaxed and called Stone a "lunatic".

"Security seemed to me to be very effective, we will of course be reviewing it and if there are lessons to be learnt we will learn them, " said Orde.

"The threat wasn't from a dissident republican . . . the threat was from a lunatic."

An NIO spokeswoman said: "Security is a matter for the Assembly and the PSNI, and all aspects are under review."

Stone (51) was charged with attempting to murder Sinn Fein's Gerry Adams and Martin McGuinness when he appeared in court yesterday morning. He faces a total of five charges of attempted murder following Friday's crazed attack, including attempting to kill two security guards and an unknown person. He was also charged with possession of articles for terrorist purposes and possession of explosives and an imitation firearm. He has been remanded in custody until 22 December.

Stone was sentenced to more than 800 years in jail after he murdered three men at the funerals of three IRA members in Milltown Cemetery, Belfast in 1988 and was given early release in 2000. It is understood that his early release from jail under the Good Friday Agreement is to be suspended.

In court yesterday, a PSNI officer confirmed to Stone's solicitor that, during two police interviews, Stone told the police that "he acted alone and that no other person or organisations were involved in the preparation or planning".

Sinn Fein declined to comment on speculation that security measures around Adams and McGuinness have been increased this weekend. A party spokesman said: "We don't publicly discuss the security of any of our party members.

There would be no point in having security measures and then discussing them with the public."