Bulgaria has pointed an accusing finger at the Lebanese armed group Hezbollah over a bus bombing last July that killed five Israeli tourists.
Tsvetan Tsevtnov, Bulgarian interior minister, said on Tuesday that two of the suspects had entered the country respectively with an Australian and a Canadian passport.
"We have established that the two were members of the military wing of Hezbollah," he said.
"They had Canadian and Australian passports ... [and] lived in Lebanon since 2006 and 2010."
Speaking after a meeting of the country's National Security Council, Tsevtnov said Bulgaria expects "the government of Lebanon to assist" in the investigation.
Following his comments, Najib Mikati, Lebanese prime minister, said in a statement: "Lebanon trusts that the Bulgarian authorities will undertake a serious evaluation of the results of the investigation, and affirms that it is ready to cooperate with Bulgaria to shed light on the circumstances" of the attack.
The July 18 bombing of the bus carrying Israelis at Burgas airport on Bulgaria's Black Sea coast, the deadliest attack on Israelis abroad since 2004, also killed the Bulgarian bus driver and the bomber. About 30 people were wounded.
Israel immediately blamed Iran and what it called its "terrorist proxy" Hezbollah. But until now Bulgarian investigators had stopped short of blaming anyone.
In the wake of Tuesday's announcement, Israel, which has been pushing to have the EU declare Hezbollah a terrorist organisation, called on Europe to "draw the necessary conclusions as to the true character of Hezbollah".
"This is yet a further corroboration of what we have already known, that Hezbollah and its Iranian patrons are orchestrating a worldwide campaign of terror that is spanning countries and continents," a statement by Binyamin Netanyahu, Israeli prime minister, said.
|Analyst discusses the accusations against Hezbollah
"The attack in Burgas was only one of a series of recent terrorist operations against civilians in Thailand, Kenya, Turkey, India, Azerbaijan, Cyprus and Georgia. All this is happening in parallel to the deadly support given by Hezbollah and Iran to the murderous Assad regime in Syria."
Both Iran and Hezbollah have denied any involvement.
The EU has been urged to blacklist Hezbollah before, but its 27 member states have so far not been able to produce the unanimous decision needed for such a move.
The bloc needs time for "a reflection over the outcome" of Bulgaria's investigation, Catherine Ashton, EU foreign policy chief, said in a statement released before it was urged to take action.
John Kerry, US secretary of state, discussed the threat with Ashton, and a spokeswoman said in Washington that Ashton "knows where we want to go".
Separately, John Brennan, the White House adviser on counterterrorism, urged Europe to disrupt Hezbollah's terrorist networks and commended Bulgaria for its "professional and comprehensive" investigation.
No direct links
The US helped in the investigation at the request of the Bulgarian government.
Rob Wainwright, Europol director, said the investigators found no direct links to Iran or to any al-Qaeda-affiliated group.
In an interview to the Associated Press news agency, Wainwright said forensic evidence, intelligence sources and patterns in past attacks all point to Hezbollah's involvement in the blast.
"The Bulgarian authorities are making quite a strong assumption that this is the work of Hezbollah," he said.
"From what I've seen of the case - from the very strong, obvious links to Lebanon, from the modus operandi of the terrorist attack and from other intelligence that we see - I think that is a reasonable assumption."
Wainwright said the bomb was detonated remotely using a circuit board that a Europol expert had analysed.
Although it was initially believed to be a suicide bombing, Wainwright said investigators believe the bomber never intended to die.
Two counterfeit US driving licences that were found near the bombing scene were traced back to Lebanon, where they were made, Wainwright said.
Europol, which helps to coordinate national police across the 27-nation European Union, which includes Bulgaria, sent several specialists to help investigate the attack.