Dissident republican groups are plotting to kill Northern Ireland Deputy First Minister Martin McGuinness, he revealed today.
Sinn Fein said the Police Service of Northern Ireland (PSNI) told Mr McGuinness that a threat to his life had been made by dissident republicans, who murdered two soldiers and a police officer last month.
In the aftermath of the murders, Mr McGuinness branded the killers traitors to Ireland and today he said the threat against his own life would not deter him from his efforts to build the peace process.
"Over the past 24 hours I have been contacted by the PSNI and told of the existence of a threat to my life. It is believed this threat comes from a so-called dissident grouping," Mr McGuinness said.
"I have spent my entire adult life engaged in the republican struggle to bring about Irish unity and independence.
"Throughout that time there have been numerous attempts made to silence me and stop me going about my republican work.
"These have come from a variety of British state agencies and their surrogates in the loyalist gangs.
"It now seems that some of these small groups have now taken their place in that company."
He added: "One thing is for certain: neither I nor Sinn Fein has allowed these sorts of threats to stop us representing our community and driving forward the republican agenda in the past and we will not allow it to deflect us from our work in the future.
"The task of building the peace process and advancing republican and democratic goals is far too important for us to let that happen."
Sappers Patrick Azimkar, from London, and Mark Quinsey, from Birmingham, were shot dead by the Real IRA outside the Massereene Army base in Antrim, on March 7.
Two days later the Continuity IRA claimed responsibility for the murder of PSNI officer Stephen Carroll in Craigavon, Co Armagh.
One man has been charged over the soldiers' murders and three have been charged in connection with Pc Carroll's murder.
In the wake of the killings the main political parties in Northern Ireland united in opposition to the violence.
First Minister Peter Robinson and Mr McGuinness led pledges that the political process would not be derailed by dissident groups who have declared their opposition to the peace process.
Earlier this week Sinn Fein leaders began a series of public meetings to outline the party's strategy to deliver a united Ireland through the political process.
The party's president Gerry Adams and Mr McGuinness used a meeting in the republican heartland of Galbally, Co Tyrone, on Wednesday to launch a strongly worded attack on dissidents.
Mr Adams said republicans should focus on policy and actions that would help deliver a united Ireland.
In a message to dissidents, he added: "Militarism, elitism or adventurism is no substitute to strategy, for tactics, for common sense."
He said some dissidents were wedded to the use of violence as a tactic while others were motivated by ego and opportunism, but he said all were wrong.
"Some take exception to remarks by republican leaders and seize on these in an entirely self-serving and negative way," he said.
"Others threaten to kill us, or they actually attack our homes or offices."
He added: "Let me make it clear that Sinn Fein is not going to roll over and surrender our struggle to any of these elements."
The Sinn Fein leaders were given a standing ovation by the crowd of more than 200 people and the party now plans to address the public at a series of other venues.
Earlier this month dissident republicans used an event commemorating the 1916 Easter Rising to make a veiled threat against Mr McGuinness, but confirmation today of the official warning from police represents a ramping-up of tension.