Taoiseach Bertie Ahern tonight said death threats to Sinn Féin leaders were being treated seriously by security forces on both sides of the border and in Britain.
He was reacting to Sinn Féin's confirmation that the PSNI has warned of a new threat to the life of party leader Gerry Adams.
The latest threat comes almost two and a half weeks after it was reported that hard-line republicans had threatened Mr Adams, chief negotiator Martin McGuinness and north Belfast MLA Gerry Kelly.
Sinn Féin's confirmation of the threat came just hours after a letter to a Belfast newspaper from the loyalist Michael Stone said he had planned to kill Mr Adams and Mr McGuinness in the Northern Ireland Assembly last Friday.
Mr Stone was arrested after he tried to launch a bomb attack at Stormont.
A Sinn Féin spokesman said they were aware of the threat from a number of quarters to their leadership.
"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 said.
"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."
Speaking to reporters in Brussels after addressing the European Parliament, Mr Ahern added: "In fairness to the Sinn Fein leadership, they never make any attempt to play these up.
"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."
Earlier in a debate after Mr Ahern's address, DUP MEP Jim Allister accused the Taoiseach of promoting a "stale message" about the stalled EU Constitution.
The vocal critic of power-sharing said: "Mr Ahern may soon be judged by his own electorate to be a stale politician."
However, referring to scheduled March 7th elections for a new Northern Ireland power-sharing assembly, the Taoiseach replied to Mr Allister: "I'll deal with my electorate and I wish you well with your electorate next year."
Earlier, Mr Ahern said in his address to MEPs that the EU had played a very constructive role in the Northern Ireland peace process.
PA