Sinn Féin president Gerry Adams has been warned of fresh threats to his life.
The PSNI contacted the West Belfast MP about the latest threats resulting in key Sinn Féin members increasing their personal safety measures.
Other threats emerged earlier this month, most probably from dissident republicans opposed to Sinn Féin's current policy on powersharing and policing.
Chief negotiator Martin McGuinness and policing spokesman Gerry Kelly are also understood to have responded to the increased level of threat.
A spokesman said the party took the threats seriously but warned its members would not be deflected from current strategy. "Sinn Féin takes all of the recent threats seriously," a spokesman said.
"We are very mindful that there are elements within the British system, within unionism and some disaffected republicans who are opposed to the Sinn Féin strategy and are prepared to take extreme action to pursue their narrow agenda."
He added: "Sinn Féin will obviously take whatever precautions we can to minimise the danger, but we will not be deflected from continuing to do the work we were elected to do."
The latest threats follow last Friday's attack on Stormont by loyalist killer Michael Stone.
It emerged yesterday Stone's intended targets were Mr Adams and Mr McGuinness.
In a detailed letter to the Belfast Telegraph, written before the incident and published yesterday, Stone confirmed he intended to kill the Sinn Féin leaders when he tried to burst into Parliament Buildings last week.
The letter details Stone's weapons which included a replica handgun, a large "flash bang" device, seven nail bombs, three knives, one axe and a garrotte.
It also details how Stone figured he would breach security measures at the main door and force his way through the Great Hall and into the Assembly chamber where he would kill his "two targets".
Had they not been present he states he would have found Mr Adams and Mr McGuinness in the party's offices elsewhere in the building.
Stone describes himself in the letter as a "freelance dissident loyalist" and makes clear he fully expected that the attack would end either in his arrest or his death. Outlining the dangers, he foresaw the two outcomes.
"One - I will be in police custody with the events surrounding my arrest ensuring that I spend the rest of my natural life in prison. Two - That I am deceased . . . the latter in all probability, as I don't intend withdrawing from my mission as I did on 16th March 1988" - a reference to his attack on mourners at Milltown Cemetery in which he killed three people. The letter bears his signature, his nickname "Flint" and a fingerprint.
Speaking in Brussels yesterday, Taoiseach Bertie Ahern said he took the threats against senior Sinn Féin members seriously.
"In fairness to the Sinn Féin leadership, they never make any attempt to play these up," he said. "But these threats are a concern. These are not frivolous threats and I know that security forces, North and South and in Britain are very alert to threats like these."