Bulgaria urged other European governments on Monday to take a harder stance towards Hezbollah after blaming the Islamist movement for a bus bombing that killed five Israelis at a Bulgarian Black Sea resort last year.
Bulgaria's implication of Hezbollah in the attack in the city of Burgas has reignited a debate over Europe's approach to the Shi'ite Muslim group.
The European Union has resisted pressure from the United States and Israel to blacklist Hezbollah, arguing this could destabilize a fragile government in Lebanon and contribute to instability in the Middle East.
Hezbollah is a major player in Lebanese politics and its support is vital to the authority of Prime Minister Najib Mikati.
Bulgarian Foreign Minister Nikolay Mladenov was expected to present detailed findings of an investigation into the July 2012 Burgas attack at a meeting of EU foreign ministers in Brussels on Monday.
On his way into the meeting, Mladenov told reporters Europe should take collective measures against Hezbollah.
Asked whether that meant the EU should blacklist the movement, he replied: "Given the fact that we've already made quite firm statements about where we believe the responsibility for that attack lies, I think the answer is quite obvious".
Other European officials have said steps short of blacklisting Hezbollah could be taken first. That could mean asking the EU policing agency Europol to coordinate investigations into Hezbollah's presence in Europe.
Much will depend on evidence provided by Bulgaria linking Hezbollah to the attack, EU diplomats say.
Officials have said, for example, that France appears to have softened its traditionally staunch opposition to blacklisting the group, saying "all options" were on the table, provided the evidence is strong.
The U.S. government said this month that Hezbollah must be held to account for the Bulgaria attack, and urged Europe and others to pursue an investigation into the incident.
Reporting by Justyna Pawlak and Adrian Croft; Editing by Tom Pfeiffer.
© 2013 Thomson Reuters. All rights reserved.