European Union governments agreed this morning to put the armed wing of Hezbollah on the EU terrorism blacklist.
It is a reversal of past policy, fuelled by concerns over the Lebanese militant movement's activities in Europe.
Britain and the Netherlands had pressed EU peers since May to put the Shia Muslim group's military wing on the bloc's terrorism list.
They cited evidence it was behind a bus bombing in Bulgaria last year, which killed five Israelis and their driver.
Until now, the EU had resisted pressure from the US and Israel to blacklist Hezbollah.
It argued such a move could fuel instability in Lebanon, where the group is part of the government, and add to tensions in the Middle East.
But evidence from Bulgaria about the attack and concerns over Hezbollah's growing involvement in the war in Syria persuaded opponents to back the move, which triggers the freezing of any assets the group's armed wing may hold in the 28-nation EU.
"It is good that the EU has decided to call Hezbollah what it is: a terrorist organisation," Dutch Foreign Minister Frans Timmermans said on the sidelines of a meeting of EU foreign ministers who decided on the blacklisting.
"We took this important step today, by dealing with the military wing of Hezbollah, freezing its assets, hindering its fundraising and thereby limiting its capacity to act."
Tánaiste Eamon Gilmore had voiced reservations about the blacklisting.
Ireland is concerned that an EU declaration could destabilise the country, where Irish peacekeeping troops are serving.